Could it work? Absolutely. The basic idea has been used for all sorts of computer/data applications for years. It's also not too far from the concept of mounting your modules in standard 19" rack hardware.

But I'm not really sure what advantage this gets you*. You're not able to move individual modules around easily, instead you move them around in groups installed in fairly large "cassettes". At that point, there's not much functional difference between a "cassette" and a small powered case. You can stack small cases to make a larger rack, and you can use them individually without having to plug them into to a larger apparatus. I wonder if 19" industrial racks or stacking smaller self-powered cases could acheive the same goal, but maybe this suits your needs better, so long as it was designed & fabricated carefully it would work.

I think you could improve this design by replacing the L-angle with perforated sheet metal bent to shape. That would be stronger and would provide electrical sheilding while still allowing airflow. I also think making the cheeks and the levers out of aluminum would look a lot better and be more durable, that little detail would make this look like something out of an aircraft or spaceship which I think would be very cool.

• I fibbed a bit when I said I couldn't see any advantages. I do think the easy access to the rear of the busboard is an advantage. My biggest gripe about re-arranging modules, especially with a large case, is that sometimes it can be a real hassle to plug/unplug modules from the busboard. Having access from the back is one way to solve that problem. However, if you're re-arranging your modules in groups (cassettes or individual powered racks), how often are you having to deal with that problem anyway?

I've been thinking about a different challenge: If one has a very large system, how to access a lot of modules without having to stand up-and-down so much. One idea that came to mind was inspired by old-fashioned lecture halls which had flip-around double sided chalkboards. A teacher would write on one side, when that was filled up and they needed more space they would flip it over and write on the other side. If at any time if they needed to refer back to what they originally wrote it just took a second to flip the board over again. A rack could be built like this: Imagine taking two racks, attaching them together back-to-back, and then having a central axle about which this entire assembly can be flipped around quickly and easily. That central axle would be hollow and would contain power cables & breakouts. The only major disadvantages would be:
a) you couldn't simuntaneously tweak modules on opposite sides of the flip rack
b) patch cable positioning could get complicated

I don't think these are killer disadvantages. Problem a already exists for large systems. Problem b can be dealt with by providing breakouts built into the rack. Some would go front-to-back between the two faces of the flip rack. Others would go out from the flip rack, through its hinge, to allow connection to modules elsewhere in the system. I'm imagining the finished product to look like an upright piano. It would sit on the floor, have 3 or 4 rows of modules oriented mostly horizontally, sort of like a desk or a standard keyboard position. These would not "flip". A vertical section would sit above, with most of it being the flip rack. A robust latch (foot operated?) would allow this to unlock and be flipped around. Part of the vertical section would be stationary and would contain the breakout connections as well as more space for modules that would not flip.

Of course, it's not ideal that you can't tweak both sides of the flip rack simultaneously. However, the trade-off is that you have easy (albeit not perfect) access to a lot more modules in the same amount of floorspace, and you absolutely can play that many modules simuntaneously thanks to the breakouts.