>>50843123A. Level scaled gym leaders, like what's implied in the anime every now and then. Might also be a good excuse to slap together a non-linear gym progression, assuming we ever get actual gyms ever again.
B. Allow more trainers/gyms to use items AND hold more stuff than just an oran berry or two.
C. Longer breaks between free healing stations/NPCs/etc., maybe you have to beat an entire gym in one run and the trainers respawn if you lose/leave (no rewards for rematches? No money for rematches?)
D. Sprinkle a few randomized trainers in random places to surprise the player.
E. Have trainers actually use AI more often, rather than spamming Helping Hand in a 1v1.
F. Stop giving away all these free items for fuck's sake, I haven't had to use an item since like gen 2.
G. EXP Share can stay, the normalfags would hate it being gone, but reduce it so all non-participating Pokemon only get like 1/3rd of the XP.
H. Force that toggle on, the one that makes it so you can't switch between fights, whatever that one was called.
I. Make most gym leaders and some trainers have good EVs, IVs and natures, especially in the fights later in the game.