They could switch to transformer cases that can be reassembled to each standard.This is not how cases work. I any of the cases I own, putting the 24 pin on the backside would mean it would be impossible for the board to fit. The 24 pin is taller then the screw standoffs so you NEED the back of the case cut out to accept this placement.
BTX already tried to sunset ATX. If you're gonna do it, you need to get all the mobo makers AND case makers on board, and it still going to take years to transition away. See also: the move from AT/babyAT to ATX.
With some thinking, it is possible without spending a lot.