Would be a nice project. Although I would like to see an A600 accelerator as they are more uncommon. I think quite difficult a project to get going.
Most feasable 'accelerator' is currently build at home using the following steps (roughly);
1. Empty the case
2. Install mini/nano/pico -itx motherboard
3. Install hardisk and such
3. Hook the keyboard to that USB interface from Jens
4. Hook up the leds
5. Run UAE and have all the speed and ram you want.
Just pretend. No but really. The A1200 has adequate accelerators around. The PPC boards with those BVisions clearly reveil you really want to get rid of the old hardware.