You do not need to change the seals if you mask them off.... The seals are used to extreme heat (hello... Porsche brakes) so do not be fooled when a place that powder coats says they need to rebuild them. You just need to mask off the pistons and seals... The inside will still be black but who cares right.
If anyone wants to do this I have an extra black set of 996 calipers in mint condition. I will tell you that $500 is to cheap for me to sell them.

 

You actually need to replace the dust boots around the pistons and Bleader screws. I am going through this process now. You will also need a air compressor w/a air sprayer nozel and wood blocks. But you are right they can just powdercoat them.

 

Doh... just realized I must of hit "new thread" instead of reply on the red caliper thread... o-well.... rough weekend