Genghis,
I may be wrong but I was always under the impression that to operate a 'multi-crew' aircraft, one must have passed theoretical knowledge to the level of ATPL subjects rather than CPL subjects. I seem to remember reading that in several different sources, including Lasor's.
As for MCC, the only legal requirement is to hold a valid IR rating. Dosn't matter whether the licence is a PPL or CPL. When I did my MCC couple of years ago, I did it on my PPL(hadn't even started my CPL yet).