Could we just follow the atx spec? There is a maximum length for expansion cards, and at that end there are optional supports. These are in servers already. Just start using all that case volume to support the GPU.
Cheers, bravo, exactly what I wanted to say. However just to be pedantic, I just read the atx spec to find this exact information and it is not there. I suspect the expansion card dimensions are in the pci spec.
My case has these and I would love to know the proper keywords to find extension brackets I could add to my shorter cards. Searching for "extender" returns electrical extenders for the PCIe port itself.