I'd be interested in this. That kind of levelling system would be fine with me, I think. As for the battle system, I'm not really sure. Maybe have it be more turn-based in gym battles and stuff with official rules, and less so in unofficial battles? I don't think it should be limited to just four moves though.

Whether Pokémon faint or die could be based on how much damage they take, I guess. Like if its just worn down and beaten, it could faint, but if it gets overpowered or hit by a strong attack when it was already close to fainting it would die?