My daily driver is a pure EV, but while I was on holiday a few months ago I was driving a Yaris Hybrid as a rental (which to my understanding is basically a Prius drivetrain in a Yaris body).
Fuck me it was terrible. Every time I applied even mild acceleration it sounded like the valves were going to eject out of the engine, meanwhile it had about as much get up and go as a sedated elephant. 0-60 in four to six business days. On ramps were an interesting experience.
The only saving grace was that we only used about a third of a tank of gas during our week long trip.
I'll stick with pure electric thanks. No complicated drivetrain with multiple systems to go wrong, no compromised performance, enough range to get me everywhere I need to go, and good enough charging infrastructure (at least in my country) to make longer journeys trivial.
Even without an official rank, on Voyager he was still considered a Department Head and (more importantly) the CMO, which gave significant authority (even exceeding the Captain on certain medical matters), regardless of whether or not he was ever given any pips. The same thing would likely apply on subsequent postings.
If he ever had to be assigned a rank for clerical/administrative purposes, it would probably be the default required rank for a Starfleet CMO candidate for the class of ship he was serving on.