Why Do it with a normal bix case.
Think heat......it's a parts killer.
With a small case you can't get rid of it.
Why Do it with a normal mobo.
A micro mobo is smaller......something has to give.
Either the parts are moved closer together or features get dropped.
Why Do it with the number of sticks that gets you the dual or triple channel full speed ram.
Think ram speed.
If you do it with one stick you'll be running single channel mode.......slow.
Why Do it with a monster single rail psu.
If you do it with a multi rail unit you best get out paper and pencil and verify you don't overload some rail.
If you want to build that unit for 300 and sell it for 400....go for it.
Suggestion........don't sell it to a friend or someone who knows how to find you.