Any decent competent general mechanic will be able to work on a converted
car. If you don't like all-makes garages, take it to a GOOD VW outfit for
nonengine-related work, and for engine work take it to a GOOD outfit that
deals with that make of engine. For modified electrics, take it to an
outfit specializing in multimake electrics. Then again, if you live in a
city of decent size there should be outfits who work on modified vehicles
anyway. With luck they'll be competent.

If a mewchanic refused to work on my hybrid because it's a hybrid, he's
admitting incompetence, I wouldn't want him to get his hands on it anyway.
a Subaru engine is a Subaru engine. Putting it in a VW bus doesn't alter it
in any way. A Golf engine in an exboxerbus is no less a hybrid.