This is keyboard #3 for me. I think I am finally there. Good feel with the Glorious Pandas (pre-lubed), good sound with a custom internal pad (poly-fill layers wrapped in tape and cut to size). Matching green metal knob from lovemyswitches (turns out knobs from guitar effects pedals fit well and come in a huge variety).
Anyway, I think I am done. My attention has been shifted to classic typewriters. I recently fell in love with the early 1970's Galaxie Twelve in Atomic Blue. (look it up, you too will be smitten). Now THAT is a mechanical keyboard!
I think the problem might be sound, because the spacebar (and pcb) would be right on top of solid material and the sound can escape to the front. I guess it'll sound very flat and no one wants to spend 300 bucks on a bad sounding spacebar.