As nice as it might sound, & I'm sure the deserters in MAN would relish the service, NCL-MAN-NCL is a NO BRAINER from the start
Unless it is part of a bigger plan to operate MAN-???, the time factor, cost & practicallities for the punter do not make logical sense, as Eastern (Air Kilroe) proved time & again. Passengers will be conspicuous by their ansence & it will be Bye, Bye Gill.....
If tied up to a MAN-BFS, MAN-DUB, MAN-GCI or a lucrative mail contract for example, there might be some merit in it, but as a stand alone operation, CP GET YE' HEAD EXAMINED!!!