I've got a bug up my arse about building a tiny intel motherboard into an A1200 case with a Keyrah to allow use of the original keyboard/mouse/joystick.
I have the same bug, but for an even smaller Amiga. Industrial single board computers are made for this sort of thing (embedding in something else). I've had a WinSystems board around for years that will fit in an A600 case, just haven't gotten to it yet. Their latest board should fly running AROS:
http://sbc.winsystems.com/products/EPX-855.cfm