I haven't seen many of the early Romana serials. He was getting rather annoyed with everything in Logopolis, though, and seemed to just want to be alone. I doubt any new Companion, no matter the personality, would have lasted long with that particular version of Four. Still, in Tegan with him from seasons 12-15 would have worked.

When the DVDs not in such high demand, I'll rent it again and check out the other commentaries.