I don't think size is the real issue here. The average Saturn game size at GameTap is 85MiB, with the biggest one at under 150MiB (and we don't even know what kind of sound/video compression techniques they are using). This is well within range of them simply improving SD card support.
Whether the Wii has it in itself to emulate the Saturn, however... I don't know. Plus, has Sega ever released emulated Saturn games anywhere? With the Megadrive, they'd already re-reselased games on a number of plaforms, including on the Cube. It was pretty clear they had a working emulator. What about the Saturn?







