The Bowser fight is definitely not feasible on the SNES. Bowser and the Clown Car are actually background objects that are scaled and rotated around using Mode 7. With the way Mode 7 works, if the cloudy sky background were added, it would have to scroll, rotate, and scale with Bowser, which would look extremely weird. If we somehow hacked Super Mario World to have Super FX2 support, it would be a different story, though.
(Also, and this is just nit-picking, but the map screen font isn't variable width.)