I just placed an order for the revision B of AmiKey! Only minor tweaks were needed, such as moving a few holes in the PCB to better fit the keyboard backplate, moving several tracks away from holes, and the pads are now slightly larger and slightly shifted to more closely match the original foil membranes. I have several damaged membranes to test against, and they all have slight differences in both size and placement of the pads and holes. Really slight, maybe tenths of a millimeter, but they aren’t exactly the same. I had to approximate placement of few holes and pads, hope they’ll fit perfectly this time.
The PCBs should arrive in about two weeks and this time they will be gold plated. Hopefully everything will be fine and revision C will be the production version with a final decision to go with either 0.4 or 0.6mm PCB thickness.
Some time ago I was looking for a cheap Amiga 500 for restoration. I found one for 60 euros. The seller said it was in overall good condition and was working fine many years ago before being put away. There were only photos from the top and it looked good though it was dirty. I trusted him and bought it. If he lied … well, I’ll have more work 
First AmiKey prototypes have arrived earlier this week! They were mainly made to check that everything fits and to check that the 0.6mm thick PCB will be suitable. It fits, but a few holes have to be moved a little. I will probably also choose a 0.4mm thick PCB for the next prototypes. While 0.6mm is fine, you could use slightly longer screws to keep the metal back firmly in place.
I have recently repaired three Amiga 500/500+ computers and they all have damaged keyboard membranes. One membarne was salvaged using conductive silver paint, but two could not be repaired. I could of course order a new membrane, but they cost around 35 EUR. I understand where this price comes from, but for two membranes I can buy a fully functioning Amiga 500. So yeah, I think they are expensive. PCB membranes are also available, but the cost is about the same. So there is probably no way to repair Amiga keyboards cheaply … Or maybe there is?