I purchased the whole pack, and was wondering if there is possible to make the following effects with those. If possible, how would you make them?
-A three-hit combo where each attack is stronger than the previous one and the third deals water damage instead of physical damage
-A cleave that deals damage to an enemy and heals an ally based on that damage (If it's impossible to pick an ally, just heal the most wounded one, or if not possible either, the whole party)
-A stackable effect that reduces armor the more stacks it has and increases the strength of one of the attacks that causes the enemy to recieve damage that also scales with stacks before cleansing them
-A transformation you can use when you have 100TP, adds an ultimate ability and finishes after either casting that ability or after five turns
To do everything you described you need a basic understanding of JS. Not knowledge, just an understanding of how things work. I like your ideas and I'm sure you can do everything with these plugins if you want to, as they give you all the tools you need.
First of all, I advise you to take a closer look at YEP ActionSequencePack, as it is the one that will allow you to program all your features in the skills noteboxes.
I really liked the idea of the hit curing the weakest ally. Since I wanted to do something similar, I wanted to make a magic button that you press to apply a potion to your weakest ally, and this is what I came up with:
It's not actually that hard, I'll try to explain:
I found in the other thread a way to compare multiple variables. This is the common event.

You will need something like that to determine what actor is the most damaged one.
In this common event variable called "lowest param" is just comparing to all of your characters HP and if it finds the value lower that it's own, it takes this value. You also have to set your character hp level to A B C D variables before activating the event, I didn't add this in the event.
Original thread where it's explained better:
First of all, I'm new here, so I'm sorry if I'm in the wrong section of the forum! I'm currently making my very first game and I wanted to do multiple endings. I thought about setting variables that increase with specific dialogue choices so that the highest variable will determine which ending...
forums.rpgmakerweb.com
So after processing that event your "ending" variable value will be from one to four depending on your most damaged character.
And then goes the magic in the skill notebox:
<damage formula>
value = $gameVariables.value(1);
</damage formula>
<setup action>
COMMON EVENT: 9
if $gameVariables.value(135) = 1
animation 8: actor 0
HP +VARIABLE 1: actor 0, (show)
else if $gameVariables.value(135) =
2
animation 8: actor 1
HP +VARIABLE 1: actor 1, (show)
else if $gameVariables.value(135) = 3
animation 8: actor 2
HP +VARIABLE 2: actor 1, (show)
else $gameVariables.value(135) = 4
animation 8: actor 3
HP +VARIABLE 1: actor 3, (show)
end
</setup action>
In the damage formula I just set the damage of the skill to variable 1.
Then I run the common event to determine the most damaged actor.
And after that goes the check for all possible outcomes. So, if the most damaged actor is
2, so after the common event variable "135" will take the value of
2. And then Variable 1 value (skill damage) will be added to the 2 character hp and animation will be played.
I didn't actually tested it, I just showed how it all may looks like since your desired skills are quite tricky, but interesting at the same time.
(Also, this code will heal your character with the "clean" damage, not counting the armor of the target and final damage. To determine the real dealt damage you probably have to set one variable value to the enemy HP before the cleave and after, and then subtract.)
So, with a little effort you can do all what you want, you just have to dive into YEP plugins functionality to gain absolute power over your skill eventing.