Speaking of the Sliger, could you fit one of their flexible bifurcation cables?
I was excited by the idea of aio cooling my GPU and cpu (ID Cooling Hunter Duet or party with custom tubing) and a capture card for a streaming/rendering box.
I know it is bit late, but have you looked at the InWin cases?
https://www.in-win.com/en/computer-chassis/bm-series/APAC
It has two low profile pcie slots.