Possible? Definitely. Likely? Probably not. It would take a lot of effort and things like internal game timing become a lot more important when having to interface with real hardware. Not to mention that it'd simply take a lot of time for a very small fraction of users.
I guess you mean two player games through the link... well since no games support that feature through the gc cable, you would first need to hack each game, not very convenient if you want my opinion and probably not possible, protocols being likely different and too complex to implement with simple ROM patches.
Also, unless someone figures how the gbagc link cable can be accessed on wii side (which nobody has done yet and probably never will), it's never going to happen.