Has anybody ever changed XKE's complicated, inefficient, brake activation system from............master cylinder with vacuum valve and slave tandem cylinder and attached vacuum booster and vacuum reservoir...............

To a modern dual master cylinder with a dual diaphragm attached single unit with built in reservoirs....?

This is the way all new Jags are equipped and so are most other cars !

This whole package can be purchased for $250...... Of course it must be matched for the correct size piston volume and for disk front & disk rear
application...........I have built a lot of cars from the ground up and have never seen such an over complicated system, with too many things to go wrong as in the XKE Jaguar brake system !