Super FX chip would've powered SNES CD "Playstation" add-on, considered for NA base SNES too

[Pemalite]

Well. The SuperFX chip was a RISC CPU, so could have been used for anything, even non-gaming tasks... Although it did include a few extra instructions for graphics duties.
I think Nintendo made the right call not including a CD attachment or SuperFX chip with every console sold, keeping it simple is often the best way to go about something.