I'm thinking it may be great to have a Davies-Craig pump in series with the EDWP.  If the belt goes away you could turn on the EWP, and fly on to an airport - maybe at reduced power - but still fly safely to an airport.

I'm not sure if you realize it, but that's exactly what I have on the RV-3.  I've run the DC EWP on the ground with the belt removed, and it did fine, so I have no doubt that it would get me home.   FWIW, I leave the EWP running all the time, since it's easier than worrying about when to turn it on.