As someone looking for a smaller NCASE alternative with vertical GPU positioning, USB-C (plus the rest of front I/O ports), watercooling capabilities and outstanding design, I must have to say that you achieve perfection with this idea Dan, my sincere admiration and respect for such amazing work.
Now, I think there's a few improvements here and there that could turn a perfect idea into a perfect product. Some are my personal preferences and by no means do I want to change your original vision, but I think is worth to mention in case you want to consider some aspects:
1.- The design and size is perfect and I already love it (including the brilliant idea of flip it in order to get the power button and I/O ports in the right, very convenient), but would be absolutely PERFECT if the default position of the radiator and I/O ports at the bottom would be right-positioned instead of left. I think most of us have the PC next to the right and it will be fantastic (with the possibility of flip over and put in the other way, off course).
2.- As a Strix GTX 1080 owner that barely fits in my NCASE, I would appreciate 5 aditional mm of room for GPU, due your size limitation (295 mm) and the Asus Strix size (298 mm). Probably it will fit, but I think 300 mm is a great maximum lenght for such a perfect case like yours, and the Strix 1080/1070 is a popular card.
3.- This is one personal, but I prefer black USB Type-A port instead of blue as a cleaner and more elegant touch for an already refined and pleasant design. I think the "wow" modern factor of the blue is no more relevant in 2017 as most of the modern cases have USB 3.0 ports in the front I/O panel.
4.- Do you think is it possible to separate the GPU to the back and put the motherboard more in the front, just like the A4-SFX? I think it will be a great oportunity to extend the GPU thickness compatibility taking advantage of the lack of CPU air coolers in the Mobo area (plus, if you have some nice AIO RGB waterblock, it won't be covered by the GPU, and might open the door for future window closed panels, as the air flow comes from below).
Aside from that, I have no problems with the radiator thickness nor fans, maybe just the color of the Noctua fans, but surely there will be other thin fans that could fit.
Keep it up with the project, now I know what would be my next case!