SuperGrafx could not have been the PC-FX in 1989 or even 1990. that would not be possible or practical.
what the SuperGrafx should have been, IMO, is something more like a "Super X68000" in a console, with a faster clocked 68000. without the floppy disc drives, with more colors on screen (4096) the same palette (65,536) the addition of true hardware scaling & rotation. maybe more sprites (say 256 16x16). something roughly as powerful as Sega's highend boards with Super-Scaler technology. a real leap above the PC-Engine, something with more power than the SNES, more or less on par with the NEO-GEO, though more reasonably priced with games costing no more than $90. also the "Super CD-ROM" should've been a CD-ROM for this SuperGrafx. the regular PC-Engine would use CD-ROM2 system card 1.0 2.0, 3.0 etc but leave Super-CD-ROM exclusive to SuperGrafx. even if only say 50 or 40 or so SuperGrafx SHu-Cards and SCDs came out, if the quality of the games remained very high, it would've been so much more worthwhile.