Have a look at this, particularly beginning on Page 31. Look familiar? Yep...3U Eurorack format, albeit with the lower fastener being taken up by a drop-in lipped rail instead of screw-in attachment points. These are rather fascinating, as they're part of a series of desks which would also allow for ample space for controllers, external effects, etc. And they can be stacked on vertical rails incorporated into said desks. Depth is 91 mm, plus you'll notice there's internal rails that can be used for attaching power supplies, distros, etc.
So...are you ready for 385 hp? Mind you, I'm betting they're not exactly bargain priced...but the possibilities for those looking to create genuinely MASSIVE builds do seem to point right there. If anyone can locate pricing data on these and their related components, do please post it.