I think making this a competition would be pretty pointless... if such a mod where to even be worked on you can assume it will not be 1 guy or girl doing it alone, considering the range of work and skill-sets that'd require
Until we know how for sure whether it's easy or hard to mod textures this is all a bit premature imo. That said, a graphical total conversion might be an interesting project.... especially for user campaigns that want a more serious and gothic style to work with.
