Based on my limited grasp of anyone after Myth, my picks would be Sana, Ina, IRyS, and Bae.
Assuming they're allowed to talk about stuff before they joined, or conversations they had as Namie and Nagu, having two people who've known each other a while at the core can act as a hard carry just in case.
You have 2 singers, 2 artists, 2 Australians, 4 different Asian heritages, and none of these connections involve the same 2 people so there's a lot they can bounce off of one another and draw from to get the ball rolling.