Pokemon now has a challenge mode, available as soon as you get the game, for "veterans of the series only". What changes would you like to see?
>Gym Leaders are HGSS tier difficult
>cannot use items in trainer battles
>you aren't told the opponents next pokemon, and you don't get a free switch after each faint
>AI gets increasingly competent, and by the end their Pokemon sets are near smogon levels rather than just the last 4 moves their pokemon learned (it really isn't difficult to make a decent Pokemon AI; there are plenty of bots on Pokemon Showdown that can battle on their own)
Of course this is all wishful thinking, so go nuts.