Regarding the size changing potions: it's very complicated, both technically and from a game design perspective. Just think about it: entering buildings, syncing sex animations - all of that is tied to character size. I do have a few ideas about it, and I personally really want to see it in the game, but I'll be straight with everyone - I have no damn idea when I'll be able to implement it.
As for everything else : it's already in development. For example, right now I'm working on the combat system. Buffs from potions could follow right after that, since they're logically connected.