So if we don't want to fight against Cis, we're going to have to make the PLI but then we might have to fight against Anna?

That sounds like a really tough decision.
OK, so, let's say Fatima has a rebellious spirit and can likely go in that direction even without being a PLI, and that Sam can be taken that way too because of his friendship with the MC, surely he can bring Anna and/or Cis too because if he's able to have and maintain close relationships with them, then they'd want to join him too, no?
If we saved Anna and have some romantic sexy time moments with her, and we also have some romantic sexy time moments Cis that build up relationships with each, even if they're not the PLI, it could potentially be a bit disappointing to put in all that work to then have them say, "no, I stand with the Terrans and you're my enemy now".
This scenario would remind me a lot of BaDIK where
the MC can do everything with Maya and Josy yet get rejected by them simply because of his Affinity score which really shouldn't have an effect since he's been nothing but good to them and built up good relationships with them. Even if we can't do everything with Cis and Anna, to be able to do at least 70-80% of things with them and then have them reject joining him would be a like this.