I like the idea of having companion centred missions. But I'd like it possible to have them end badly for your relationship with the companion; Zaeed's probably being the best example of this. Generally in ME 2 if you did the loyalty quest then you got the companion's loyalty whether you wanted it or not. The same thing applies to the companion quests in DAI (I'd have loved to have been able to find Vivienne's tomes and then sell them, for example). In ME 2 this meant that it was pretty easy to get the best ending in the suicide mission just by completing game content - which I intended to do anyway since I paid for it!
I'd like to be able to complete all of the content related to a companion regardless of their approval (romances excepted) and I'd like companion quests to have the possibility of both positive and negative consequences.
I believe you can give Viv a regular Wiveryn heart for her boring "Loyalty Mission" but it does not really change anything. Maybe force us into more difficult situations such as...
-Marine Guy: Captain Pathfinder, my little Sister is on a ship that broke up in an asteroid field but there is one life-pod left. Its damaged but if my sister and the crew is in there...
-Captain Pathfinder: Of course! I'll reroute us there, then after we save her we'll bang ok?
-Pilot: Captain! There is a Quarian Vessel under attack! We can intervine but we have to act fast!
-Marine Guy:What about my sister?
-Quarian Crewmember: *Bursts In* Captain! We have to save that ship and crew! They have important data and stuff!
-Marine Guy: There may be as many as 30 crew members in that lifepod and that Quarian ship is mostly automated. Ten crew Max!
-Quarian Crewmember: That lifepod is not even broadcasting! They're Dead!
-Marine Guy: We don't know that! Captain please!
-Captain Pathfinder:...
Obviously it would alot better written that my poor excuse of an example but conflicting interests of squad members could ensure we're never best friends with everyone, creates conflict and tension between crewmembers and between the Player. Combine a couple Loyalty missions and make us choose between squadmembers. These could effect friendship and romance arcs too. Sort of like in ME2 between Jack and Miranda or Tali and Legion where they would argue and we'd have to pick sides (Only in ME2 they gave us a third option that made everyone happy) only now it would come in the form of a mission with no "3rd options". Just a suggestion.