Just sharing my opinion, but I'm not really into changing trainers too much. I feel like having trainers just give you money would be fine because:
1: you can choose what to spend it on
2: it's like the normal game
3: if kingcoin feels like putting in department stores like they have in all the games (i think) then you'd need money
Obviously the third reason depends on what kingcoin decides to do about that idea but i feel like trainers who give you items wouldn't be good as a replacement, but maybe those kinds of trainers could go in towns, where they say "I'd bet you can't beat me! Want to battle?" then you say yes or no and if you win you get an item and possibly a good one.
If he does add department stores i suggested they have stock of items so you can't buy anything you could possibly need, instead they only have some ultra balls and special pokeballs, some medicine items, some evolution stones and only 1 of the ones there are, some tms and only 1 of the ones there are, and some held items and only 1 of the ones there are.
btw what is going to be done about mega stones and z-crystals. I wouldn't really care if they weren't included in the game, but i think they would be good to put behind cut trees and rock smash rocks etc. along with the better held items. I think hms should be used to get special items and go to special routes or caves where there could be legendaries, so they're optional, but you're rewarded for using them.