If possible on the OSSC Pro, I feel Split Screen or Picture in Picture option could provide some useful utility. The ISL51002 does not seem to be able to receive multiple analog inputs at once, but the additional HDMI port may allow for dual input.
A 2 console split screen could allow options such as 8 player Mario Kart Double Dash, or side by side Tetris vs. games on a single monitor. A PIP set up could allow a smaller secondary screen, such as a GBA screen in Gamecube connectivity games like WindWakers Tingle Turner, or Crystal Chronicles player HUD.
I understand this may not be possible, but felt it could be a fun usage of the hardware, even if a little out of the intended scope.