I really wish more Mini-ITX boards came out that allowed GPUs to be horizontal so it could fit in a 2U case. Unfortunately making it vertical makes it 4U, negating the size advantages of Mini-ITX.
So I actually "repurposed" a riser cable from an old ITX build to slap it into my primary proxmox server to play around with home-rolled VDI. Surprisingly, it worked. If you're feeling bold you could try that route