I suspect it will be possible, but modelling and animating a new character is a process which requires a lot of time and skill
Well I've seen some mods that prove that the 2nd thing isn't always required, but time and detication certainly it is.
It makes me think of the movie "grandma's boy" where a guy models, animates, programs, and play-tests an Xbox game all by himself, with a "good collision" engine and fantastic particle effects. Not very likely.
