The PIO board/case is great, although I don't understand why the ASRock board is bigger than Mini ITX. It still has only one slot, so why make it bigger. If you're gonna do this, you're aiming for SFF.
And I am disappointed by the size of the RVZ04. 3.8L is too large for that concept. ASRock's own design is 2.7L, which is frankly too large as well. You wanna aim for less than 2L with that design, as small as 1.2L is actually possible, tho that is a bit extreme. At 3.8L, you can actually have a full-on Mini ITX with a short card strapped to the back of it, so what's the point of spending a pile of money on an MXM card if you won't get something tiny.
Sorry to be a debbie downer.