Hello,
I have been toying the idea for 2 years. I have already precisely measured the connector spacing of my A1200. I also reversed engineered the keyboard schematics.
For those who want to measure the connector spacing on their A500 or A600, it is quite easy : use a flatbed scanner to scan the backside of your Amiga PCB and then a tool like Gimp to measure the spacing between connectors.
Regards,
Frederic