Nami and Mila seems actually the unlikeliest one, because Mila's said she's not into girls. Vic and Maja is 100% certain NOT to happen, because patreon - Maja's path was dropped to lewdable only rather than an LI (maybe Ocean's rethought it) because Maja will choose Vic's happiness over her own, and it's impossible to have a shared path.
Nami has already shown that she will prioritise Nika's happiness over her own, and will accept Bella even if she's snarky about it. Her acknowledgement of Bella being able to bring Nika out of his shell/introspection shows that she can see the bigger picture. Bella has nothing specific against Nami. We already know Nami is bicurious, so the questions are (I guess) whether:
- Nami will actually accept being the third wheel,
- Bella is into polyamory AND girls.
Everything else is just conditions - ie Nami getting over her need for revenge (she has a short enough attention span anyway), Bella either being open to sharing or developing a liking for Nami beyond mere tolerance. I feel their throuple will be inequal, and only exist because neither Nami or Bella are willing to give Nika up, but I imagine they will be uneasy, while Vic is totally open to sharing by the appearance of things. Throuples with Vic seem a done deal.
Anyway, gotta see how fast Nika can reach maturity and make a mess once again first