I don't do portraiture much, and when I do it isn't studio-based. Even so, in my opinion, the more lights the better!
I have an FL-50R and there've been plenty of times where I would have loved to have had another flash or two. I'm thinking of eventually getting some FL-36R's as backups to the FL-50R.
Anyway, your plan sounds pretty solid to me. (I don't have much experience with multiple flashes and portraiture, though, so if someone with more experience writes in and has a different opinion, I'd defer to them.)