Then a little bit of something floating around in the bilge goes into
you pump impeller and you have an unpowered sinking boat instead of a
powered sinking one. Great.

If you're screwed, you're screwed. Powered or not.

Besides, a raw water pump doesn't have a fraction the capacity of this
rig.

No argument there. But then nor does it have the constant horsepower drain
that pump incurs.