Honestly, for the Pokemon I most want to play as (Marill/Azumarill), I may have to hope that the company will set up generic trainers as sync pairs, since I don't recall my favorite used by major trainers. As for trainers themselves, I would definitely take Miror B. Hoping Orre gets some representation in this.
EDIT: Best I can hope for is probably Lyra, the one that is a friend of the MC in Gold/Silver, as a Marill is that character's primary Pokemon, I think. If Anime characters get added in, then perhaps Tracy.