Well, ps2 shouldn't be to difficult. Since the PS2 is 128 bits and the GP32 is already 32 this only leaves 96 bits to be emulated!
A 4gig PS2-DVD could then be transfer to a 128MB SMC card. You just have to rip out some stuff.
As for the joypad, since they make PS2-to-USB converters then could also make PS2-to_GP32USB convertors.
The emu author should also provide us with a hardware dongle so I could use my PS2 memory cards on the GP32, because I already have a lot of game saves!
The only REAL problem I can think of is that my PS2 lightgun is a PAL lightgun and the GP32, being korean, is probably NTSC. This would mean that you can't play PAL lightgungames!!!
And if you can't play PAL lightgun games on this shitty emu then I don't see any point in building it!
(sorry.... long, hard day in the office while its 25 degrees outside
)