Saturn would be quite possible if it was made officially by SEGA, since they would have all of the knowledge of the platform, as well as professional programmers. Unfortunately, no one in the homebrew community has proper PSP devkits or that much knowledge of the Saturn. The hardware of the Saturn was poorly designed and overly complex so even though graphically and hardware-wise it doesn't have anything that couldn't be done on the PSP, it is very hard to emulate since so little is known about the inner workings of the hardware, which would be needed to produce a more efficient emulator. This is why you can't even emulate the Saturn at any great speed on a modern computer. It's actually harder to emulate than the dreamcast (Chankast runs at full speed on about 1.5Ghz, Cassini (or any of the others) probably wouldn't get full speed on anything short of a supercomputer.
Dreamcast is just as powerful as the PSP, if not more so. Therefore it would be ABSOLUTELY IMPOSSIBLE to emulate. It generally takes a computer at least twice as powerful as the original machine to be able to emulate it, especially if it is a homemade emulator rather than an official one (Virtual Console on Wii, Popstation). I do however wish someone would make some Dreamcast ports to the PSP. Crapcom, king of re-releases should port Marvel vs. Capcom 2 and Street Fighter III to the PSP (actually those would technically be arcade ports but they were released for Dreamcast). And of course Jet Grind Radio FTW:) .
Please correct me if any of my technical information was wrong.
