I tried making a faceplate using the clear PCB technique last year. Copper foil epoxied on Perspex and etched. Kinda worked. But I decided to go with laser etching/milling instead.
Thanks for the pointers, I might try perspex with some sort of stick on tracking & glue to hold the components in. I am thinking of through hole & the electronics off this board on a more conventional circuit board.
I think your best bet is to laminate copper foil to your substrate, then etch.
But, you might be able to etch the silver coating from a mirror with a suitable etchant. Then, conductive epoxy to attach the surface-mount components. I've never tried it, but it might work... The silver on the mirror isn't very thick though, so it wouldn't be able to carry much current.