i think the easiest way is to give people choice of the a500 or the a1200 MX board. Both should be physically identical (once i sort out the LED issue) The A500 version will prob be a little more as that will have the built in controller. whereas a basic A1200MX board does not and simply needs the 31 pin connector.
If you want the a500 version for an A500 then that will have the LEDs and the PIC controller on board and you will connect to the motherboard via the regular 8 pin header. The USB option will be available to connect to PI etc.
If you want to be able to play with USB on your A1200 then it is probably better to get the A500 version with no LEDs and use either the PLCC option or the REV2b connector.
If it is just a straight forward A1200 KB replacement then the A1200 version using 31 pin connector is for you which has no controller and no LEDs.
This can all be specified when buying.
