Why not taking Nicholas and Herbert/Knous? Different classes so you can push them fast to +7, plus Nicholas with 100% accu refill will benefit a lot from any of these commanders.
At the moment I see Nicholas as even a better commander then Rick. He hides himself very often and also another team member, plus he has the cross atk curse which by itself can change any battle. Between Richard and Nicholas is a very close call for me, but Nicholas has the advantage imo. Better base stats, plus the combination of his special is nuclear.

As for Murometz, I don't see him as that useful commander. Yeah he can lock and increases s-atk, but comparing to others specials he's like a kid. Better go for offense until you can get Aldebaran. Above Murometz I think I'd still go first to Hayley, cause she'll also help you once you go for Aldebaran.
Also you might still have to factor in WC event and choose more than one.

At the moment what is costing me the most is that if I am lucky at WC event I'll have to probably decide by taking out my Caroline in favor of Nicholas and Richard...