Very nice work you're doing there ! Your work reminds me of my approach : clean and repaint everything !
The only suggestion I've got , is that you use DOT 5 Silicon brake fluid . The K-H 4 piston setup is infamous for hanging pistons up due to corrosion ( regardless of how vigilant one is with brake bleeding ) .
I'm happy to see that someone has stepped-up to the plate on K-H 4 piston brake calipres / parts for our beloved A's !
Kudos to Rock Auto !