A couple of project digit boxes linked would seem to a potentially superior replacement to the 4090s: https://www.nvidia.com/en-eu/project-digits/

4090s now all ready for their waterblocks and installation in the 10x GPU server:

For the black system, the internal radiators are now removed, 2x new GPU (6x total) and new distro board and quick connects to all components are fitted:

Next one almost ready to go

It does need some more parts to fit the quick connects though.....