There's a couple floating around Toronto's ST scene, and they do perfectly fine. Basically all it does is flash a different ROM onto the CPS2 board so that you can play another title when you want to switch games. Feels like an Everdrive for CPS2.
But since the ROMs run on the real hardware there's no emulation issues. If you're wanting to play more than just ST, and don't want to go board hunting, this is the way to go.