You're trying to annoy me again, aren't you? <mumble> hole in the hood... </mumble>
FWIW, I wouldn't do the spot caliper again. If you need it to make a vehicle pass a safety inspection then maybe. I'm not really happy with the clamping power.
What calipers do you have now? Is this a configuration you were already using? Sometimes if you use a large caliper in the rear it can be really hard to get the brake balance right even with a proper proportioning valve. The difference in flow rates reaches a tipping point and the vehicle is really sensitive to loading wrt the brakes. In a flattie that might not be that big a deal.
As for commonality between all four corners, I think it is worth sacrificing to get the correct braking balance provided both sets of calipers are commonly available. The next time I do this kind of setup I'm going to either make the ZJ/WJ drum e-brake inside the rear disk rotor work or use a GM metric caliper with the built in disk e-brake. IMO the key is keep a rough proportional flow rate and swept area as used by the OEM. Example for the WJ, do the math for fluid flow rate, pressure, etc. between the front and rear brake calipers and try to keep that ratio of caliper size between the selected calipers. In my case I ended up with WJ front brakes and Suzuki Sidekick four door front calipers for the rear brakes. The Sidekick caliper is pretty close to the WJ rear caliper but I wanted to match the rotor I am using (also Sidekick) to the caliper.