I went a different route.
On my first playthrough, I decided that every person was going to go and help on one loyalty mission. So for the 12 loyalty missions, there are 23 people. (Kasumi's is just you and her.) So, each person goes twice. (except for Legion who is last to be recruited and is my last loyalty mission.) For deciding the parings, I tried to just find the person who balanced out my Shep and whoever's loyalty mission it was.
For my second playthrough, I simply brought along the person who had the previous loyalty mission. That way I could immediately allocate points (I bank some away for their loyalty power) and test out the new power. Plus, that ends up giving each person 2 missions again.
For my 3rd through 5th playthroughs, I'll just bring along whoever the LI interest is for that game. So I can see all the dialouge and because that's just how I want to rp it for those playthroughs.
Haven't figured out what I'll do for playthrough 6. Maybe just throw darts at a board with names on them...