What if I just had the motherboard in suspension? Like have the case split in two, possibly with hunges, and then the motherboard can just be taken out?

Attaching the PSU+drives to the lid of the case looks like a good idea, too, but should the bays be attached to the lid too, or just to the case sides?

@rkelson: Killer case! I don't think it'd fit here, though ;P

The problem with "just" taking the motherboard out is that it's attached to a bunch of cables--both internal and external. Because of this, it's more convenient for the motherboard to stay in place and to move other components out of the way. In a typical case, the PSU and drives are mostly out of the way already, but if you want a compact "cubical" format, then this mostly isn't an option.

One possibility if you want a two-story layout with mostly fixed components is to put the motherboard on the second floor (as in the original plan), and to have both the roof and front of the case removeable (they may be in one piece). This splits the computer into two air chambers. With the front and top removed, it's easy to get at the PSU cables. However, the drives probably need to be in a removeable tray to get at their cables. This layout can be convenient if you don't anticipate upgrading your drives. Also, airflow in the lower chamber is very cramped. You need extra height to give the PSU some intake room and to provide air gaps around the drives--the end result is less compact than the single chamber "hinged" suggestion.

I guess it'd be better to go with a vertical case, or put the motherboard on the bottom...

I was thinking of putting the mobo at the bottom, but how much space would need to be between the CPU & drives? I was thinking of putting a fan at the front or back of this case section, to help the airflow. Maybe putting the PSU on the top level, or maybe on a third level on the bottom, with holes in the ceiling by itself, holes on the ceiling to help cool the rest of the floors. Stupid idea? Good idea?