That would be fine - and/or the swappable installation mounts could simply use multiple medium storage batteries, which, while heavy, are basically man-handle-able. Pulling out a folding small lift is easy in any case.
As for engine and frame work (the parts that should ACTUALLY require a full lift) all the garages should have built in hydraulic lift stations as a matter of course. It’s unlikely that looters would have made off with multi-ton pieces of fixed heavy machinery. 
As it stands I end up dragging around a boom crane in cargo and just glue it to a stand-alone heavy frame whenever I need to do work, which while functional, is a bit silly unless you were actually broken down in the middle of nowhere.
Right now it’s just really inconsistent which sorts of installation/repair work require jacking (should really only be tires), lifting (should mainly be frame, engine, and other large undercarriages installs, such as tanks, permanent batteries, etc), vs. things which shouldn’t require any assist (internal compartment installs, boards, ceilings, etc).
Frame work, while it SHOULD require a lift realistically, probably shouldn’t just for game-play reasons - but all the undercarriage and engine installs should. I suppose you could forgo a lift for frame installation up to a certain weight limit (say, up to the approximate size of a large ATV) after which you need a lift to go any larger.
Frame removal or repair probably shouldn’t need a lift regardless.
