Trust me, cooling both gpu and cpu with a 240mm rad is more than enough.While I should be upfront and say the chances of me ever buying one of these is minimal, I really like the concept. Having space for the 360mm radiator makes this a great candidate for a fully water cooled custom loop setup in a very small footprint/volume - cooling both a CPU and GPU from a single 240mm rad is ... functional, but a 360 is a lot better suited to a setup like that. Looking at your renders there might even be room for a small pump/res combo at the top above the GPU, without having to resort to exotic PSU options or other means of eking out extra space. I like it!
I tested it with an Overclocked i7 8086K @5GHz and an Overclocked GTX 1080 Ti @2050MGhz cooled by an 140mm Monsta Rad and it was all good with both stressed to the maximum with Aida 64. So a 240mm Rad should do even better.