Yeah, that would be cool. But the N64 CD drive was actually planned, but Nintendo thought it would be too expensive. So they lowered the funcionality a bit and made it into a hard-disk drive that was essentially a big memory card, but even that was only released in Japan, and it didm't last very long.
As for the SNES CD drive, Nintendo actually chose not to go with Sony for the add-on, but instead got Phillips to make the craptastical CDi, which actually warped the SNES' plastic parts with its sheer amount of suck. Of course, the "Nintendo PlayStation" was a really cool idea (a dedicated CD-based 32-bit system) so Sony manufactured it as a stand-alone product, the PlayStation. Rumor has it that Sony chose the wierd X, Circle, Square and Triangle buttons over the more conventional A, B, X and Y buttons to further set it apart from the SNES.