Hau'oli Gym - Hau if it's a sequel or Ilima if it's an AU
Heahea Gym - Lana
Paniola Gym - Kiawe
Konikoni Gym - Mallow
Hokulani Gym - Molayne
Tapu Gym - Acerola
Po Gym - Plumeria
Seafolk Gym - Ryuki
(If Hau is allowed, that's four Title Defense challengers and four Trial Captains. If not, there's no particular balance/reasoning other than what I feel works and is interesting.)
This doesn't include any of the Kahunas, so they're all able to be in the Elite Four - I mean the actual Kahunas, not Molayne, Acerola and Kahili.
