Take a look at where the spacebar switch is on the non-flipped spacebar. It's in column 7, looks to be precisely. I'm not an expert, but I would guess that if you were to put a switch hole in column 6, right next to it, you would at least have a spot to put the spacebar. You'd still need to decide before you solder which orientation you want the spacebar, but you won't need to rework your layout.
You can put a cutout there on the cad file by putting a 1u switch in the position you want.