@Crom00 - Loriano has the hookup for plastics (because he does it for a living), maybe you two could collaborate or merge designs and base them on mini-itx form factor able to accomodate an internal power supply since MikeJ said the power hookup would be a 4 pin molex to the board... This would also go along with the ATARI ST theme, since it too had an internal power supply...
@MikeJ - Any chance of getting a metal backplane cutout for mini-itx made? This could help the case designers Crom00 and Loriano and lower the cost by one large pane of plastic... or give a whole host of standard mini-itx casing options to the mases that already exist and would only need a cutout metal backplane to be accomodate your board to them... Would seem to be pretty cheap to manufacture at any machine shop where they work with sheet metal.