On the Home Barista Forum, user Matadero210 is posting running progress reports from an heroic effort to machine and construct the perfect espresso machine:
Robo-Pavoni ; learning to make espresso machine from scratch (via Make)
The design itself: take a Pavoni head, build an adaptor to connect to normal plumbing. Add a machined plate with water inlet (this is a plumb-in system), thermometer, and heater. Mount all in a brazed steel base.