I had three roos together doing well, then removed one for a few days and was never able to put him back. The two that are still together are doing "okay" but I am starting to see little bloody spots on their combs. Not sure if they are fence fighting with the other guy, since there is just chain link between them, or if the two roommates are fighting. When I am with them I don't see them sparring or posturing, so not sure what is causing the comb damage.
If i was going to separate the roos into smaller breeding groups, I would not rotate them that fast, maybe every few months, so I could see who was producing better with certain hens, but that is just me and I like to cause myself a lot of extra headaches by tracking pedigrees and performance. Comes from breeding horses and dogs for years. sorry. If you wanted the hens to be fertile at all times from both roos, then yes, swithching them every week would work.
A 3x3x3 cube would be too crowded for long term keeping of a group of CBM's. Fine for a single roo, and toss a hen in with him for a few days to get her bred, but for long term you would probably have problems. Especially with more than one hen. I would imagine pecking and canibalism would be a short step in such a small confinement.