You would prefer a diesel engine, which could run on rendered biomass if need be.
Vs. creating a rendered biomass pipeline to feed an extremely fiddly engine with hundreds of moving bits and bobs?
The fiddly engine's moving bits and bobs will degrade with use, so it should be possible to pull replacements from disused alternatives.
If The Shit Hits The Fan for reals, you can just plug in any power source to an electric motor and make it go. Adjusting power can be done with really simple electronic connections. Just an on/off switch will do in a pinch.
Good luck trying to find a head gasket for a certain model of ICE though =)
These ones do. You're probably thinking of brushed motors, like the kind you can buy at Radio Shack as "hobby motors". EVs typically run brushless or induction motors, which require sensors and electronics to time the power to each coil.