I tried to squeeze an 800MHz Mini-ITX into an old A1200 Case...
The Mobo fits (with the connectors at the back of the A1200 case where the Real Amiga Mobo would have them), the Hard drive fits, the Slimline DVD fits into the old Floppy location, even a small 240V to 12V (~4 Amp) PSU fits!!!!
But the problem is the DIMMs, they are too high, they stick up too high and no keyboard will fit. There isn't any other way you can really fit everything in sadly :-(
It would have been great to run AROS on, and the TV output is ideal!!! I wantedtoshow off at Wold of Amiga Shows, for having the only 800Mhz Amiga1200 :-D (and one with 18bit Audio, DVD drive, 30gig hard drive and 3Dgfx, all in a standard case)
As for the Amiga Keyboard... Kronos's idea of using a PS/2 keyboard contoler and rewiring the amiga keys to it is actually the best idea I've heard on the subject (though it's going to be sooooo fiddly... best do it when you have some time on your hands), my personal idea was to use a BasicStamp microcontroller but that would have been a pain in the butt.
