The issue with DZUS (1/4 turn) fasteners is that they don't have any adjustment range, to speak of. They're designed to hold two panels together that are already touching, with separation loads limited to a few pounds at most (the pressure it takes to insert/latch them). The weak spring in the load circuit will allow a heavy load to bounce around, fatiguing and possibly breaking stuff.
I share the OP's frustration with spinning wing nuts on long threaded rod; I'd be sawing off the thread leaving enough for minor height differences among batteries, and using hex nuts. At least with those, you can spin them off with a deep socket & a drill or impact driver.
edit: another option with wingnuts is to use a spacer, cut from rigid tubing/pipe. Another piece to lose, but would minimize the spinning routine.
My personal go-to is a sectioned stainless worm drive hose clamp. A section gets riveted to an angle bracket for one side/top, and the worm drive + short section gets riveted to another strap/angle. Fairly long adjustment range, and can be tightened/loosened with a nut driver, and opened completely for battery swapping.
*If* one side of the battery is exposed enough, and an actual latching system is really important, I'd look at
adjustable cam latches like these; just one example from ebay. Would require adapting to or replacing the existing hold-down posts, of course.