I'd almost rather go through the JPAC so I could more easily swap between my SSF2X board and the dreamcast.
If I managed to run it through the JPAC thats all I would have to swap.
If I hack a VGA cable I have to swap that, as well as still converting the controls through the JPAC.
It looks like what i'm trying to do is managable but it might end up being a bit more confusing than I was hoping