I don't think heads on pikes is re-writable, exactly. It's either text, a non-gore version or a gory version. Or it's just not in there. And maybe it doesn't have to be, but I think really I'd rather let the story dictate what happens than try to force the direction to go somewhere else instead.
And the MPAA rating is actually more confusing than the ESRB rating - there's less of an indication as to what separates one rating from the next. (The ESRB is confusing bc it talks about degrees - how much bad language or suggestive situations tips a T rating into an M rating, they don't say, but at least you know it has to do with those things. The MPAA rating is so vague as to be almost useless. Worse still is the way the ratings are assigned, but that's a whole other can o' worms.)
I think I'll just have to do my best to come up with a storyline that won't have too much objectionable content (or at least, the type that would get it a higher rating). The idea that I had is probably just going to be too adult, even tho there's no blood/gore, nudity or the like.