Mr Angry,
The volunteers are not being brought in to replace the striking cc permanently. They will be brought in to get flights to their destination, working alongside experienced crew.
There will be staff from various departments who cannot voluteer, for several reasons, such as being below the minimum height requirement. I'm guessing here, but the offices will operated with skeleton staff for a short time, and that is do-able.
Personally, I think a flight with 5 experienced cc (777) and a pilot, an engineer, check-in agent, a baggage loader and a waterside manager sounds like great fun.
Gg