Wow, Tesselator. Just be sure you aren't working on a big project at the time - I got the same itch, nothing to new and needed a new, better case for my old SFFPC; moved it into the new case, then *ka-BAM* - guess who forgot the jumper configurations

. I did not make the thing, somebody else did, and I could not find out the motherboard manufacturer for the life of me... On the bright side, it gave me an excuse to buy a completely new machine a week before my project's deadline.
But to the OP, I think that to do this you would need a case which is bigger then the MP case to begin with - you might want to take measurements of where the MP mobo screws into the case, and then try to machine a new backplane out of sheet metal and attach the new backplane to the old backplane in as many places as possible.
My largest concern lies with the daughterboard - personally, I do not know how well it is supported by itself. Doesn't it lock with the MP case somewhere