I don't know if your idea would work, but I do know that I have a keyboard adaptor sitting here, aimed at A1200 computers for usage with an external keyboard (A2/3/4000 keyboards) and it has it's own controller chip on the board.
The board has a ribbon like the one going from the A1200 desktop keyboard and into the white socket. And it has connectors for LEDs aswell, so any tower LED would work with it :-)
