Although Pamtre are the highest level berry for Beauty, in the originals, Kelpsey berries were the lowest level berries that could be used to evolve Feebas. Speaking of berries, I wonder what role the Berry Master will play here. Not that the Berry Master was ever really that important, but I think his wife was the only one to ever give high level berries like she did. I'd imagine that if compost bins were to return, then they would either be in his field, or around the flower shop.
My guess is that the Berry Master will actually run a Berry Field garden. Since Gen III a few new Berries were introduced and maybe instead of making them available they could make them into Berry mutations.
New Berries added since Gen III were: Occa, Passho, Wacan, Rindo, Yache, Chople, Kebia, Shuca, Coba, Payapa, Tanga, Charti, Kasib, Haban, Babiri, Chilan, Micle, Custap, Jaboca, Rowap, Roseli, Kee, & Maranga.
Roseli, Kee, & Maranga are the most notable as they have not been given Contest condition stats, having been introduced this gen in XY.
Also let's not forgot about the e-Reader berries, would be neat to see them made into Berries: Pumkin, Drash, Eggant, Strib, Chilan, Nutpea, Ginema, Kuo, Yago, Touga, Niniku, & Topo.
Ginema, Kuo, Yago, Touga, Niniku, & Topo are notable since they never got English names. Names are based on the plant they're based on: Ginema is based on an Onion, Kuo an Okra, Yago a Bitter Melon, Touga a Chili Pepper, Niniku a Garlic, and Topo a potato. Yago and Topo can probably keep their names (A Bitter Melon is called Goya in many places), but the rest would need to be translated (how about Onin, Arko, Chilp, & Garic?).