(...would love to see 25mm thick fans top & bottom, so one could use Corsair ML120s all around...)
I would have also liked this, but using slim fans at the bottom was necessary to keep the proportions of the case a perfect square. The Noctua slim fans are fantastic in this build by the way, and keep the whole case cool with general cross-flow ventilation.
If the chassis dimensions were increased to allow for 25mm fans at the bottom intake, then the resulting extra depth of the chassis would allow for a wider variety of AIOs... I would look to the Fractal Design Celcius S24; with the fan hub on the unit & the wiring from radiator to pump totally hidden, it would make for a very clean install...
And with 120mm x 25mm Corsair ML120s all around, the noise profile would stay consistent & there would be the option for LED / RGB Goodness top & bottom...
The extra 10mm or so in depth would also allow a bit of a gap from the front interior of the chassis and the butt end of the GPU, a little more room for airflow & better cooling...?!?