12V? Not possible with repro antique bulbs, and the high amperage would make it worse, IMO. We're talking maybe 20 or 30 bulbs around the walls of a room, near the ceiling. I'd guess around 1000 watts total.
*Personally*, I don't see why there would be a problem with this in common sense terms. I'd simply mount the sockets at 7ft (same minimum for equally-dangerous ceiling fans), use a box in the wall as normal, and have some sort of decorative fixture to transition from the box wiring to the cleat wiring.
Since it's only for a 'mock historical' installation I'd talk with the local AHJ and see if I could convince him that it could be done safely. If they're mounted at 7' above the floor he might be amenable, especially if there is adequate code-compliant wiring to serve the needs of the room. Maybe if he can see that there would be no temptation to ever touch or tap the cleat wiring he'd let you do it.