With all these new abilities, I'm starting to think that it'll be pretty cool to "change" you mon's ability with a new mechanic. I've always found annoying abandoning the mons of my first run 'cause of bad IVs and abilities (especially starters and legendaries), now that the IVs problem is solved, it could be cool to do the same with the abilities. Of course not any random ability, just changing between a number of limited abilities (now we have 3 at most for each pokémon, I'd say 4 would be a good number of potential abilities for each pokémon, excluding signature abilities and megas). Of course changing the ability too soon could be game breaking, it would need some kind of limit, but it's easy to control, maybe permitting the change at level 100 as for the IVs, or just getting the new mechanics after completing the story.