The Yellow and Blue pumps are interchangeable.
The blue elec pump u/s is non-dispatchable so it is quite common to swap the serviceable Yellow for the Blue, non main base, to dispatch the aircraft.
Dual Engine failure high up would be within the windmilling re-light envelope therefore EDPs still available, if you dropped out of the envelope would you not attempt an APU start for more puff anyway thus giving you the electric power for ACMP? Being in engineering have no idea on the QRH/FCOM procedure.
As for the flow/delivery rate of the electric pumps, I regularly retract the Aircraft undercarriage (on jacks) using the yellow pump through the PTU, bit slow and whines a bit but it gets up there!