Let's see..
Can we please please please please please please please please please please please get some new Alolan Forms that AREN'T KANTO. I love my Alolan Ninetales, but come on, we need some Pokemon that aren't Kanto to get some attention.
Can we make SO battles less tedious? Maybe it's just me, but I think they could make it so Adrenaliine Orb starts a chain. That way, Pokemon constantly don't have to be calling for help.
Gyms and Trials? Here me out. If this is an "alternate universe" what if we had it in which we do trials to get to the gym and the Totem Pokemon is the Gym battle? Just a thought, but I feel with the empty lots they have in SuMo, it could be possible they're doing something?
Have a difficulty setting and maybe? They probably won't do it at this point but it could happen.
Fix the Non-linerity a bit? Open up some more space on the map and have more places to explore.
Finally..a national dex..nuff said.
That's it for me really.