Sorry for late response, life...
Yes, this case relies on indirect airflow similar to Corsair One. That case being a proof-of-concept, I believe this case would also work fine. I'm however no expert on things liquid cooling, so any educated opinion on the potential of this case and potential pitfalls, I'd appreciate it.
I am below posting a SketchUp model of the case layout. Clearly, the success of the negative pressure idea will require that the case is as sealed as possible except for where the radiators are installed (also except for the top, duh). A single-slot-bracket GPU would work the best and thankfully most new generation ones do not require double-slots.
Other notes are that the CLC loop pretty much requires flexible tubing. Based on my knowledge in physics of cooling and the case layout, a loop as Pump -> CPU -> GPU -> Rad240 -> Rad120 -> Pump should work the best. I also have the case thought-through (but not fully modeled) using 1.63mm thick Aluminum 5052-H32. This case should arrive at 315x315x100mm = 9.92lt. I shall call this, Model 1 (see below).
[MEDIA=sketchfab]1319d353bced4a7b85446fd24a072120[/MEDIA]
In the mean time, I also came-up with another case layout using almost the same components but at much smaller case dimensions of 306x307x85 = 7.99lt. I shall call this one, Model 2.
What Model 2 foregoes is the thick (PE series, 38mm) 240mm radiator in favor of the thin (SE series, 26mm) version. However, it now sports two 120mm fans with direct airflow through both 120mm and 240mm radiators. Oh, and Model 2 supports only single-slot GPUs, but that shouldn't be any concern with most modern GPUs. The only caveat with Model 2 seems to be that the pump+res unit is now installed horizontally. The manufacturer claims it should operate just fine in that orientation, but I'll leave the discussion on potential handicaps to more experienced audience.
So, here is Model 2:
[MEDIA=sketchfab]5f4f71823a1b4234beb1d044409196a1[/MEDIA]
Full details on Model 2:
- 1 x EK CoolStream SE 240 rad (280x120x26)
- 1 x EK CoolStream SE 120 rad (160x120x26)
- 1 x EK-XRES 100 DDC MX 3.2 PWM or similar size pump+res combo
- 2 x 120x25 fans
- 1 x full-length GPU with full-cover block (one-slot thickness and bracket)
- 1 x FlexATX PSU (81.5x40.5x150)
- 1 x miniITX motherboard
- 1 x 2.5’ drive
- Airflow relies on two things: 1) the top 120mm fan to create negative pressure and preventing any heat build-up, 2) the bottom 120mm fan is to create a wind-tunnel through the radiators.
- Only both sides of the bottom 120mm fan is to be perforated.
- Case is to be manufactured using 1.63mm thick Aluminum 5052-H32.
- Considering tolerances, the case outer dimensions are to be 306x307x85 = 7.99lt.
- CLC loop is to be Pump -> GPU -> Rad240 -> CPU -> Rad120 -> Pump
Between the two, I certainly favor Model 2, as it achieves a much smaller volume and favorable proportions. It truly would be a console-style case with 85mm thickness. It also requires much less perforations. Plus, the positioning of the GPU enables using a clear side-panel (or a clear window) to display the GPU 
Any comments?
