First off, make it on the Switch. The increase in power is good, as is getting off the sinking ship that is the 3DS.
I'd say 80 new pokemon, as well as 20-30 new forms of pokemon, mostly new evos but maybe some regional forms. Most importantly add in a normal type eeveelution with Protean.
Starters should be Grass/Ice, Fire/Rock, Water/Fighting
Make the game more open, while still going back to the gym format. Have the choice between tackling gyms in a bit of a different order but not too much, something like having the 4 gyms open after the first two, able to be challeneged in any order, scaling to the amount of badges you have.
A more desertlike region seems best, something like Egypt. Have it have mostly Johto and Hoenn mons, some Sinnoh stuff too but not much, just the good standout designs.
