I really doubt this could be handled by a Wii. The Wii has roughly the same horsepower as the original Xbox (From what I understand) and the Xbox could barely handle Half-Life 2. Also, this is a PC game, and would have to most likely be completely rewritten in order to be run by the Wii.
That is unfortunately mostly correct. Although the Wii (no official specs have been released) is in that range of horsepower, it's enough more than the Xbox to run HL2. I don't think too much would have to be re-written and if it is a lot, out-source it (get the pun?) to the talented Wii homebrewers who would give up their lives to make this happen.
Also, I think the orignal xbox version was poorly ported (Valve is not great with consoles) because the system requirements were fairly close to the specs and PC
games use less power to run than advertised because PCs also run background services (as you may already know), whereas a console has just about no things running in the background meaning all of the RAM and processing power goes straight to the game. Sorry for the rant and I know you may already know this The SSL but,
this is for every new person who needs to know.