Shame about that power brick. I do sincerely hope that isn't actually a proper PSU stuck in there since that would duplicate the 3.3 and 5v components that already exist on the picopsu they are using (ie. wasted space).
Frankly, I'm getting tired of the continued existence of huge PSUs in the first place. Considering you can get 500W Flex ATX PSUs and 700W SFX PSUs the full size seems overkill even in a desktop, and yet it's still kinda hard sometimes to find a small case that actually uses the smaller PSU. Not many cases use smaller PSUs since there aren't many to slot in, and not many small PSUs exist since it's hard to find a case that supports one (excepting brackets)
Anyways, looking at how AMD put this together to sandwich a combined CPU-GPU waterblock reminded me of a Thin Mini-ITX board Giabyte made a few years back that had an x16 slot on the wrong side of the board. If someone came out with another one of those with more recent specs, you could do the same thing but actually have the back of the GPU and motherboard facing the same way rather than having to run cables for them. Of course an actual Thin Mini-ITX isn't wholly necessary, just having most of the upper I/O row clear for a full height card would be enough.