1. Ash portrayed as the strong, veteran trainer he supposed to be 2. Ash to have a rotating roster 3. Two rivals: an experienced trainer like Ash and a newbie who gradually gets stronger 4. Some friction between Ash and his traveling companions, similar to what he and Misty had 5. Rivals for Ash's companions and arcs that are actually developed 6. Team Rocket back to how they were in the first half of BW, albeit with more personality 7. Ash capturing his pokemon the old fashioned way instead of always having to win them over first. Like how he caught Pidgeotto. 8. A quicker pace 9. All of Ash's pokemon fully evolved by the time he reaches the pokemon league. At the very least, any pokemon he has that have 2 evolutions should be in their second.
I have more, but I think these are at least doable without changing the show too much.