I think Dashkid is talking about OpenMugen, which is open source but has been discontinued in a pre-Alpha status:
http://openmugen.sourceforge.net/
http://sourceforge.net/projects/openmugen/
I think the best option would be that Pandora will ship with a custom light-weight firmware, but Ubuntu "Pandora Edition" could be downloaded from openpandora.org. As Pandora will be able to boot from NAND and SD card, you use the default firmware (very fast and efficient) when you want to play...
I think out-of-the-box Wiimote support would be awesome, but I didn't thought about Sixaxis... Why choose between Sony and Nintendo when you can have in Pandora the best of both worlds ;) ? If the Wiimote and Sixaxis support aren't built in the firmware, I hope developers add support for both of...
Puck said in gp32spain forums that the D-pad has 4 "contact buttons", but the plastic doesn't let you press "opossite buttons" (left/rigth - up/down) at the same time.
I will use TV-out a lot, so I would like lots of games and emulators with Wiimote / Wii's Classic Gamepad support. It would be great an emulator (or game) using the Wiimote as a Mouse or a lightgun and using several Wii's Classic Gamepads for multi-player games.
I have a mobile with wifi (and bluetooth, of course) and I use it as a "standard wireless router" with my laptop. I'll be able to do that with Pandora too, but using bluetooth instead of wifi would save battery or it would be worse?
A GP32 / GP2x emulator would be useful for the few games that aren't ported to Pandora. However, if it is possible, it would be better making a port than playing that game in an emulator: you could underclock the Pandora an save battery.
I'm doing some tests with the wiimote and my laptop (Kubuntu). It looks very promising and (as javaJake and KRH said) should be easy to port them to Pandora, but it would only make sense if they are played on TV. I'd like wiimote drivers were included in the firmware, but I suppose Nintendo...