I really do not want to see PT with key items, i think that is a waste of his character, we have Villager using items and that is dandy.
The key items have very little to do with Trainer, as well. They get him through the game, but they arent by any means the point of the game, or Pokemon at all.
Summoning and CATCHING pokemon, that is the trainer. So pokeballs and pokemon, that is what id want him to be. If somehow they including training, such as the training of pokemon in there, then that could be pretty great. Given all the customization in this game, I think that could be a unique feature; either by having different pokemon customizable into his summons, different TMs into his movesets, or flat out ways that he trains his pokemon while on the field to alter them slightly (where he has a healing pokemon, a stat switching pokemon, a sleep enducing pokemon, etc).
Hell, he could even possibly have pokemon play off of each other, double summoning to pay tribute to double and triple summons- where the strengths of each play off one another to really give more strategy into the games typings, or abilities, or the items they hold, or--- I Mean--any of the other plentiful features in the pokemon games that the single pokemon in SM4SH dont alone take account for.
There are so many options between typings, movesets, double battles, contests, competitions, items, calendar, gender, breeding, olympics- there are many ways to incoporate the strategy of pokemon into the strategy of the trainer. Super missed opportunity not to have him.