OK, just been thinking about this problem for a bit and my best idea so far is to use a "double-decker" design. 2 hashing units, side-by-side, with the other two sitting on top. Allows for a cube type case, allows 4 intake fans (or perhaps just one big box-fan) and a very simple, straight-through airflow. Might not fit in a standard rack but it's incredibly more efficient and clean design.
Yeah, I'm thinking along these lines too. Just buy some off-the-shelf (boom boom!) shelves, power supply in the middle shelf, one unit on each of the other shelves with inlet fan fixed to the front. Cool as a breeze!
Could easily mod something like this to the right size for unit + heatsink.

I think I miss all the DIY gpu rigs

#modyourjupiter
Plenty of space in this:

Hmm, you mentioned this before. Have you thought it out?
- Isn't the airflow going to be all over the place in such a big case?
- Are you going to cut and drill the hell out of it to install inlet/outlet fans? It's gonna look a bit funny.
- Does it still work as an arcade machine? If it does, probably won't for much longer when it starts to fill with hot air.
- It's quite a big thing to have sitting around in a house, especially if it doesn't work. I'd want to keep the whole thing as compact as possible.
But on the upside, no one is going to steal something that big and awkward. I hope you change the name on it to "Bitcoin Invaders"
