Splitting calipers is not a huge deal. Rebuild kits are readily available.
In fact I don't see how they could be rebuilt properly without splitting them. I use a cylinder hone on my calipers bores. Done it that way all my life. It cleans and polishes the bores so you won't have any stuck pistons. I also polish the pistons with 600 grit paper with a little brake fluid added. I have a set of metal letter stamps. When I'm taking the calipers apart I number the locations of the pistons by stamping a number or letter on the inside body of the caliper next to each piston.
You can use one of these stamps in the bottom of the piston and it won't hurt anything.
That way the pistons get back in the bores they came out of.
I also scribe a mark across the spacers between the two halves so they can go back the same way.
What you might want to do is order the square cut o=rings that are used inside the calipers where the two sides join. In my case the calipers also have a spacer to make the caliper wide enough to fit the vented rotors. (72 3.0CS) The calipers for the vented rotors have 4 square cut o-rings.
Someone said they are available from W&N.
I don't have the size but this place may have them. These are square cut.
http://www.mcmaster.com/#o-rings/=irupd1
Anyway on the reassembly you just need to have everything extremely clean. Brake clean that comes in a can with nozzle is great for cleaning.
It also dries very fast.
When it comes to assembling the two halves find the respective parts and use a little brake fluid in the bores and on the seals before you install the pistons. Get all 4 pistons installed and then find the spacers and match them up to the proper sides.Use some brake fluid on the surfaces. Clean and install the 4 bolts through the two halves.
Tighten these bolts just enough that the spacers can be moved around so you can get them flush with the edges assuring a proper alignment. Carefully tighten each bolt to hold them in place.
There is a tightening sequence. If you're looking at the caliper from the side and the bolts are across from left to right tighten the two inside first then the outside. Each number is a bolt L-R 4-2-1-3.
FYI-The binder manual says these are stretch bolts and should not be reused.
I used them again and have before. You do what you think is best.
BTW ask your plater, he probably has a way to cover the bores and other holes in the caliper for plating. They do it all the time.
HTH
Gary