Even once you've done that, how are you going to present it? "Standard" animation? I don't really think that would absorb viewers; I felt that the movie already made that way was very flat, somehow (aside from the plot mangling). There was no visual depth to draw you into the story. Of course, it does have a casting advantage. The characters look any way you want on screen, so you only have to worry about voices.

Live action? Well, without CGIs, you run into major casting trouble. I just don't think you can make a terribly convincing Ent, even with Animatronics. With CGIs, the expense would be astronomical, and you still might fall short.

"Toy Story"-style animation? This may actually be the best bet. Remember how that movie managed to achieve a very good sense of virtual reality? It wasn't exactly like the world outside the movie theater, but it was *internally* consistent. In essence, that's what Middle Earth is --- an internally consistent world that bears many parallels to, but is not completely congruent with, our own world. The elves and dwarves will look just as real as the humans within the movie reality. Again, the drawback is that the animation will be expensive. Still, limiting "name" voices to two or three characters (say, Robin Williams as Bombadil and James Earl Jones as Gandalf) would help trim costs.
Anyhow, those are my musings on the movie idea. I know others feel strongly on the subject; does anybody else think the "Toy Story" style is "as good as we'll be able to get"?

Luned