I'm gonna stick with a more simplistic route. You will create your characters with a distribution of stats, very much akin to D&D base character stats. At various points in the RP, these will determine whenever you can (critically) succeed or fail at a given event. Or these could even involve the very skills characters have, giving them alternative options, like lock picking, or being able to read an ancient language, etc. Stats will initially range from 1 (pathetic) to 10 (at the human limit). As the story progresses, your characters can and will increase those past their natural limits. And if they don't, then they will die in quite one-sided fights. And honestly, I'm that confident in my GM abilities to involve dice rolls (yet).

So, for example, a mage with extremely low charisma trying to get past a security checkpoint will make the entire town go into high alert, whereas if he had some social skills, he could just walk past the guards instead of saying something incredibly stupid. Or a character with knowledge of mage history could potentially discover some plot elements way earlier by finding some sort of lost historical artifact. Or a character with extremely high strength can just bash through the super-protected door, bypassing intricate locking mechanisms altogether. That's the plan, anyway.