Interesting, some one has released a hacked together version of GeexBox for Wii. Its pretty unstable and tbh not usable, but the video playback seems smooth and looks correct, a fixed MFE basically - but I hate the menu system, keyboard or not, the point of a media system on the Wii is to be able to do everything with the WiiMote, otherwise you may as well sit at your computer!!

You asked for ideas, so how about this:

For the fast forward/rewind, lock the Wii pointer to one axis and use its position on that axis to control speed forward and back, like a scrubber (ish).

Store a .idx file alongside the media being played that keeps track of playback position when the file is closed, giving the option to resume where you left off. Could also be used to indicate how many times something has been played or if its been played at all - useful for a dir that may contain 24 eps of a series and you forget which you need to see next, etc.

Favourites dock - an auto show/hide dock (OSX style maybe) where you can just drag and drop items to a favourites list, which can be accessed from the dock its self

A button that when pressed causes the Wii to dispense hot-chocolate and biscuits, maybe even popcorn (although I know popcorn is hard to code).