I think he meant non-standard rather than non-linear. Systems that allow the player a little more choice in how their character levels.
That being said, I am a huge fan of low level caps and of specialization. I think a lot of RPGs recently (esp cRPGs/Western RPGs) give characters the ability to do EVERYTHING. Like you said, it's pretty unrealistic for a player character to become a god (unless that's the premise of the game). I'd prefer to have a character (or characters in a party-based game) who each have a specific role, preferably one that I get to choose, and then I have choices to make to continue to grow them within that role until they become the best ____________ they can be. This also allows the designer to make sure that the different roles play off of each other well and to give players in-game bonuses for having a great well-rounded party, or a highly specialized character.
Just my two cents.
People don't play Farmville, etc for "grinding," they play it because of the very carefully crafted challenge/reward/challenge loop. Also, the majority of those gamers are looking for a casual experience, not the deep, immersive role-playing experience of an RPG. Most players agree that "grinding" is awful because it's forcing the player to complete the same task, or a set of similar tasks, over and over with very little benefit and very little variety of play. Most people who do play MMOs play them for the social aspect, the grouping, and a similar challenge/reward/challenge loop that those casual games provide. "Hey, I beat the new raid and I got this awesome gear and now I can show it off in game! I'm so cool! Now, I want to get the next awesome loot!" If the game devolves to essentially button mashing to cycle through battles to reach some ridiculous level cap, I'll tell you right now, I'm probably going to put down your game and so are a lot of other players. With all of the options out there now, players will drop your game and look for a more rewarding experience the instant you don't give them a compelling, interesting experience. As far as MMOs goes, this is why you see a massive spike in players when a new one drops, then a mass exodus a few weeks later.
I hope the OP chooses to do a low level cap and I hope that that low level cap becomes a creative challenge for the player to find other ways to make his or her character powerful and interesting than just grinding XP. I'd def. play.
This system sounds really interesting, too. I enjoy most systems that question why a certain genre convention exists and looks for a way to deconstruct it and make a more interesting or at least different play experience.
If that's what was meant, then it's the fault of the poster and not my fault. It is still incredibly linear no matter how you look at it, only opening up and allowing you to do more than your very carefully crafted stats the devs wanted you to have at that point until close to late-game when you can choose to grind for more stats or just beat the game. I opted to just beat the game and only travelled something like 12 spheres into the next persons' grid. You really didn't need to do anything more than that. Don't get me wrong, I loved the Sphere Grid. It's just, it's an incredibly linear system that merely exists so that you can have "infinite levels" to be gained. It was created, essentially, to get rid of any sort of level cap altogether. Though, final stats for everyone by the time they finish the entire grid are going to be 100% the same as a result.
I played Farmville to something like level 40 before ever getting tired of the INCESSENT grind of the game. It is grindtastic. it's so grindtastic that there are items you can purchase for real money to ELIMINATE some of that grind. Things like vehicle upgrades, fuel, farm hands, etcetera. It exists to eliminate the grind that the game carries, which is... all of its gameplay. At the point of level 40 it became "this takes too long to gain new levels, finish projects, and requires too many friends help to continue playing". Once you figure out that "more fields = faster levels", you've essentially discovered that the game is non-stop grind that plays itself. It's "do two hours of grind, come back in eight more to do that two hours again". Not very fun for those who NOTICE grind. But for other players who don't notice it, quite enjoyable. Most facebook games tend to be one version of grind or another that limits how long you can play in order to get you to buy stuff with real money. But, that's the nature of the beast.
Also, if we're going to talk about MMOs and their constant grindtastic nature... Let's go visit WoW which is SUPERGRINDTASTIC to levels I've only ever seen in games like Runescape. Oh, WoW tries to hide these grindtastic things, but anyone who has spent 6 years grinding away in games like Runescape can easily and instantly recognize the BS nature of grindtastic games pretending to hide grind. WoW has raids. No guarantee you'll even get a good drop from completing them. So, you'll do them a lot. Oh, and you'll need a guild to get through most of those raids as well. So, you'll be doing these raids a LOT to help out everyone in your guild who was kind enough to help you out. That is, IF what you needed, dropped on the first attempt. Oh, did I forget to mention that anything of real value in a game like WoW requires HOURS upon DAYS upon MONTHS of grinding to even obtain? That, or insane luck. There's a reason I never got past level 10 anytime I attempted to play it. Let's not even mention the Quests which are ALL "kill x number of monsters" or "kill this monster until it randomly drops this item x amount of times". This is not a quest, this is grinding, it's also unnecessary. Let's also not forget that 90% of all of your experience WILL come from these grindtastic quests instead of simple monster murdering. Kill the 30 polar bears for bear butt hides, that'll net you about 100 xp... Turn the butts in to the quest giver, it somehow gives you 1200 xp. Yeah, thanks for creating a system that is designed to waste the time of all who play. Now, we get to the real meat of it... How many people are STILL PLAYING WoW? Despite all the annoying insane grind? How many have MULTIPLE CHARACTERS? Clearly, people enjoy repetition and grind if they can later brag that their e-penis is bigger than someone else's. That's what a MMO does. Grindtastic to get a digital doohickey that you'll only use for more grindtastic things in the game just so you cave wave it at other people you know and impress them. Why do you think so many mounts exist in that game? Mounts who are all basically identical (there are some that aren't, but we're talking like 90% are identical), but they're everywhere. They are for bragging rights and nothing more. Now, here's the fun thing. If WoW was a solo affair... That is, nobody else played with you or could play with you, and you had to play it solo... How good of a game would it be? In about 20 minutes, you'd notice how grindy and nonsensical it is. You'd notice how much story is simply ignored.
As for MMOs being played for the "social" aspect. I'd have to argue that such a thing would really only be valid if you were trying to say those people are morons. Now, that's nothing against standard MMO players. I enjoy MMOs too. I don't play many of them anymore for lack of time or because they're all super grindtastic... But, I do enjoy well-designed MMOs and play those. If you had EVER taken a look in any given chat box in an MMO, it's filled with so much spam, that a normal player wouldn't bother typing into it 'cause nobody will see your message. Random trade junk that doesn't need to be said, millions of guild join requests from random people just clicking on you cause you wandered into town, tons of raid speak and people standing around for hours on end trying to get a group together to go for a raid, or wait for a raid to even reset or restart, money scams, beggars, people buying or selling characters/accounts, etcetera. This, my friend, is not a social place to be. We're not even getting into all the sexist and racist comments that you frequently see in MMOs either. If you're playing an MMO for the "social" aspect, with all of that stuff going on in the chat... You're either an idiot or a liar. Now, if we're talking "clans" and "guilds" and all that nonsense... It's honestly more standing around and waiting with people than actually socializing. It's also number crunching and MMO speak. Again, this isn't really socializing. I would expect actual socializing to be "hey, how are you doing? what's going on? let's go kill some monsters together while we wait for our clan to get online to do that raid". But, that's very seldom what it ever is. I'm sure there are examples to prove me wrong, just like there are exceptions to every rule... But almost every MMO I've ever played, that's my experience. I tend to quit them fairly early on because of it. If an MMO does have a real social aspect or even actual RP channels, I will stick around longer. But, most do not. Most are filled with spam and garbage. Not really a game to play for a "social aspect". I actually get more interesting conversations out of my Xbox Live than I've ever gotten on an MMO... And that's usually talking to just random people. Granted, it tends to have the same amount of BS... But at least there's a possibility of a decent conversation or meeting someone awesome who isn't obsessed with what they're playing at the moment.
Okay, now that I'm done with that rant... Let me cool down some and try to address some of your post without flying off the handle, ha ha.
Personally, I think level caps and specializations have their place. I don't mind a low level cap if it's executed well. Most games do not execute it well, so I don't place a whole lot of stock in it. If you play a 100 hour game and reach the level cap of 30 a few hours before the end of the game, it's executed well. Or, if you don't reach the level cap before the end of the game, it's executed well. If, however, I hit level cap (as I do in SO MANY FREAKIN' GAMES) before even the halfway point of the game, then I fail to even see the point of limiting my level other than a designer not knowing what they are doing, or being incredibly lazy in production. If they couldn't even be bothered to make sure I'd hit cap only when close to the end of the game and not before the halfway point, what faith should I even place in them as game designers? It's a rookie mistake that AAA titles shouldn't make and so often do. I also do not mind specializations if executed well. However, the problem you tend to have is specializations lead to everyone playing the game exactly the same. They roll with the Holy Trinity and nothing else. Even if they hate the characters who make up the Holy Trinity, it's what they roll with, 'cause it's the most effective team the game offers. Tank, DPS, Healer. A proper game designer would let every character shine no matter who you chose to bring along with you, regardless of specialization. Most games aren't designed this way. More laziness or just people who don't know what they're doing. Some people enjoy the Holy Trinity, some don't. I carry little animosity toward the "holy trinity". I do carry some apprehension in game developers using it and failing to see that they can innovate it somewhat. This is one of the reasons I liked D&D 4E so much... Whatever class you picked... It was only effective if you were an advanced player and knew how to exploit the crap out of your character... Or if you were a newbie and took some of the listed builds. The listed builds were hyper-specializations of your class, made to fill a specific role. You characters only really excelled when they were that hyper-specialized. Most games don't do that. Generally, it's just easier to avoid anything that has a "holy trinity" if you're looking for any kind of innovation. I don't always avoid these things, but I do enough so that I don't feel like every single RPG I play is exactly the same.
The initial concept of my game was "Is it possible to create a game where every single choice matters in a way that no other game has ever done before? Every choice changes the story? Can it be done?". With that simple concept, I started trying to deconstruct other stuff within the RPG world. I decided it would be better if players had to earn their stats and equipment instead of just bashing monsters over the head. I decided that while classes could be hyper-specialized, they could also be extremely customizable to allow players smarter than me to find builds for characters that worked better than I had initially planned. I decided that gaining levels should exist, but only as a means to measure what you'd have access to, and these levels wouldn't ever shut you out of content, only open up more convenient content. I decided to make my system entirely Quest based so that players would be immersed in the story and their choices as often as possible instead of worrying about combat and stats as much. I also decided that Quests could be deconstructed somewhat in that there should be the option to outright refuse Quests and never have them offered again, that refusal was a viable option. I also decided to deconstruct morality systems and try to make a playthrough as either a good or a bad person equally viable without giving either side any kind of advantage. The things you can come up with when you just try to challenge what's already out there and ask "could it be done differently?" instead of "what is the best way to do it?" or "what do players prefer?". The curious will always flock to something new, the impressed will stick around.
You see, it doesn't matter how you design your game, as long as you remember those two rules. Create enough curiosity to get people to give it a try. Once they're there, impress them with what you've created so that they stay. Even if all you have is vanilla icecream for sale, if you make it the absolute best vanilla icecream in the world, people will come back for more of it.