You may think pessimistic, but I call it experience of having retrofitted or upgrade 1U and 2U servers and it is not easy. They are puzzle and everything has to be just right.
Going as you are trying to go, I have this ASUS board (which I think is already taller than 1U) and finding a case for it is something we have told you does not work unless you find rack mounted cases which build specifically for Asus.
Even with 2U cases it is a struggle to get the board in. With the ram height, often you can't close the lid on 1U servers.
As for the Dynatron Turbine designs, we have tried those, but you also need to have the power to bring in air to feed that. The whole thermal dynamics is not a picnic, well that is if you want or need machines that have to run a couple of years with no down time.
If you must have 1U, I would suggest you just go and get a Intel server or Dell ready made server that fits your needs. They have done all the maths, worked out all the assembly issues.