You hit the nail on the head there, though. Maintenance requires parts stocks or reliable suppliers, and people to do the work. Class 1s don't want either of those; it costs money. What they want is something that has as many parts and procedures in common with the other stuff they run. If it were possible, they would have a single type and manufacturer of locomotive in their fleet. Of course, monocultures are efficient, though they're seldom sustainable, even in mechanical systems.

Even in the battery locomotive game: GE and Progress both build what's essentially a diesel with a big battery replacing the engine and generator. For ordinary running maintenance, they should work with normal procedures. "Fueling" is a little different, but with actively managed regeneration like GE's units use that hassle can be minimized - the battery unit just makes the diesels in consist work a little harder at times if recharge is needed and there's no handy downgrade ahead. The biggest users so far, though, seem to be short lines that live on heavy switching in large industrial and port areas (there still is some of that, even in LA).