The riser cables look delicate and likely to introduce latency. I think mainboards, particul;arly ITX, could have PCIe sockets on the back or on the edge, and/

The riser cables look delicate and likely to introduce latency. I think mainboards, particul;arly ITX, could have PCIe sockets on the back or on the edge, and/or at right-angles - for example you could mount a GPU on it's side next to the mainboard, plugged into a right-angled socket on the edge of the board.