Yes, so the companions you acquire have some interest in the quest. It makes sense, doesn't it? Unless you recruit a mercenary who's only in it for gold and doesn't care about what you do, so long as he's paid. In that case, the relationship can develop in regular ME way - be nice and he likes you, be mean and he's strictly professional.
The storylines we've seen thus far have to do with saving the galaxy from Saren/Sovereign, Collectors, Cerberus/Reapers, so pretty much everyone would have a vested interest in it.
Individual quests are a different deal.
It all depends on a story and companions, of course. However, I do believe that it will lead to more interesting characters and larger roleplaying potential.
It depends to some degree on how you roleplay. The more defined NPCs become, the fewer roleplay options I have.
I think the Quarian/Geth decision is a great example wrt how the various companions might react. If both are considered to be sentient species equally deserving of ongoing existence, then how would the writers define follower's reactions?
- Could be purely pragmatic if you believe one side would provide stronger support in the reaper war.
- Could be friendship based, for those characters who have developed some affection with Tali (or Legion) in the course of the trilogy.
- Could be based on choosing organics or synthetics
- Could be based on specific actions taken by Quarians or Geth
In a decision like this, I think the game would need to provide notification of not only approval/disapproval changes, but also the reasons for the follower's reactions to the PC's decision.
Where the game needs to provide x opportunities to gain or lose approval, the writers would need to assign a reaction to every follower, which tends to make them much more black/white, less flexible, less nuanced. In such cases, characters can become more like archetypes than actual people - because actual people are nuanced and don't always have strong opinions about everything.
Different strokes, I suppose.