The simplest solution would be just to add all companions to your “party” when you’re at camp. We already know the UI can handle it.
You could even have a quick screen when you leave camp which lets you change who’s in your team (like Mass Effect or Dragon Age). That would encourage people to mix things up a bit and think about the best team for each mission
This.^ So this!!
This is exactly how I would want it done. Yes it works so very well in the DA games, and, as you correctly point out, it incentivizes us to reevaluate our party composition every time we leave camp and not just lazily keep the same group always.