Well, it seems to me by looking at the list in the OP, that there are three masters that can be shifted around. This Unfinished Magus that's paired up with Saber, Mamoru, and then my master, Richard. So, the options following that principle are: Richard and Benkei, Unfinished and Roland, Saber and Mamoru. Or: Richard and Saber, Unfinished and Benkei, Roland and Mamoru. Both of those alignments would give everyone someone different on each pairing.