Nice project, but why you dont use a normal itx mainboard? With 45mm high will fit a normal itx board too. So you can use full pcie x16 and more options on mainboard, ram and cpu parts at the same dimension. I am very exciting of the temperature in games.
You should make a second test. Cause in your new setup are 2x 120mm fans for 2x 240mm rads. so i think you should make an test with one 240 rad and one 120mm fan. only so you can see how much better 2x240rad+ 2x120mm at semipassiv mode works as the one 240mm with mountet fans
I am not sure but maybe the current case design can fit small matx boards too if you dont fit the top and bot fans? Or are the case not high enough for an matx board?
Edit: damm ;) i see then you need another back plate
Here you can see the psu in the dan a4 case: https://smallformfactor.net/forum/threads/evolv-shift-shrinked-dan-a4-rules.8450/
But i think you cant fit the fan under the psu. Maybe with custom cables :) of you had an gpu with backshield you dont need use the plastic plate