In that case, "what if" you put together a SNES cartridge with 32 Megabits of DRAM and a CD-ROM controller and hooked up the CD Audio output to the cartridge port audio mixing pin and wrote a sweet looking and useful BIOS? I'd like to see a homemade SNES CD project.
I have a brilliant idea. What if I created a cable that attaches from the Game Link port of a Gameboy to the expansion port of the SNES? Then, with a properly coded stub on a Gameboy cartridge, I could send output to the Gameboy as a second black-and-white screen. I have a feeling that this could totally be used for new, innovative gaming experiences and definitely not for cheap, annoying gimmicks. This could work just as well in reverse too ;-)