'Should be doable' applies to all enhancement chips; it's simply a matter of dedication, time and endurance to pull through. That, and probably money in this case.
The Sufami Turbo hardware is laid out to link two games with each other; I doubt that there's an easy way to implement Sufami Turbo games working (with their link features intact) without programming the Sufami Turbo itself.
And, if SuperFX implementation is already questionable to suceed with the current FPGA, is it really too far-fetched to consider a new board revision to have enough free-space covered for future (possible) enhancement chip implementations?
I mean, the SD2SNES already supports almost the entire Super Famicom/Super Nintendo library, plus Satellaview and MSU1.
Might as well go full-tilt and do everything, right?
Hopefully, I don't sound too demanding. I don' t mind waiting a decade for this to happen, but if the SD2SNES can really support the entire SNES library, it will render any other flash card obsolete.
Wouldn't that be a good thing, having an all-purpose flashcard that can do pretty much everything at that point?
At any rate, that's just me.
I'm fine with my current SD2SNES, but still, it makes me wonder what will happen to the SD2SNES in the future, if the FPGA is completely filled with code and such.