I think we should demand a new form factor from the industry. now we have 64 lanes chips and 44 lanes chips and the size of the motherboard is not enough for all those lanes.
Lets assume we have 4 GPUs , this will take 4 slots with 8 slots spacing. and then we need 4 more slots (intel 44 lanes has 12 extra=3 x4 slots , and AMD 32 extra lanes (four x8 slots) .. so we need total of 8 slots .
the 4 GPU slots must have 2 slots spacing and the other 4 single slot spacing . so we end up in 8+4=12 slots Cases and motherboard standard.
and we call it SuperATX ?
SuperMicro made a similar motherboard (7 slots not 8) , but we need to standardize it ...
Actually, the formfactor already exists. It's called ExtendedATX. I believe that a specification for it was included on the www.formfactors.org site, but the site is not working right now so I cannot verify it is (still) there.
You are correct, however, it's usage is pretty much restricted to workstation and server designs. Even a full-size ATX tower chassis is not deep enough to fit this board size.