I think the key to a true Batman on film is maintaing the fantasy within limits. I think that's one of the reason's Burton's films worked so well and Schumachers didn't. The other thing is the level of stylization. Again, Schumacher went to far.
Now I believe it could be done 300/Sin city style, but the key would be to have a strong script and presentation, so that the visuals and the story become a whole, rather than the visual style jar the viewer out of the film or be a distraction as someone earlier put it. Even still, you could only take the fantasy so far, without resorting to the overuse of CGI or having Batman do things that go far beyond mortal men; i.e., Batman I would imagine is perhaps a level or two above an olympic level athlete, he isn't Spider-man, so he shouldn't be jumping ridiculous distances, etc., etc.
Following along the lines of the story being key, Batman the detective--not five seconds of spying on someone, etc., etc. A real Batman detective story--yet this is where the question, "Who are we targeting with such a film will", have to be answered. Because as I've read a few times on this board and others, not everyone will be thrilled with a "detective story" Batman. Will such a movie make alot of money?
while I do think it can be done, there would have to be limitations to prevent the film from crossing into the absurd. The presentation is the key.