Why not revert Ash to his common behavior of bickering with the team girl and not tolerating any inconvenience? One thing that's been consistent since gen 6 is him being relatively stable even when he's not in control, it's not 100% of the time and has certainly lessened in gen 7 but kids, especially young boys, definitely have it in them to be angry or mean.
Isn't the point of this character to relate to the customers who buy the game?