Bb, I wouldn't rule out that idea
entirely. 
Morm, the time constraint argument is indeed something I didn't mention in the initial post. I don't think it applies here, though. Treebeard wasn't actually in the book too much. He had more than enough time given to him in the movies. Treebeard's not a deep character; he's someone who audiences should
just like, simply because of his nature. Like a grandfather figure, almost. There's no real explanation needed for him; indeed that is shown in the book when Merry and Pippin immediately feel a liking for the Ent.
It actually took time – they went out of their way – to show Treebeard in a negative way.
*Note* – I don't think the Ents were
terrible or anything, just not that great. If you want to argue that the book-Ents are 'not that great' then go for it. I know some of you wouldn't mind...
