I seem to remember full 747s departing LHR during the strike without many cabin crew on board at all! One SCCM (not necessarily an existing cabin crew member), a handful of experienced crew and the rest VCC. Now that the VCC are experienced, we could feasibly depart LHR with no BA employed cabin crew on board.
As to the 'virtual airline', it's a great plan on paper but has anybody ever actually made it work in the real world?