STW, Hobbits would only be 20 feet tall on screen
I don't think the actor would have to 85 pounds, just very thin and in costume. And like the other hobbit actors, shrunken proportionally in size. And be athletic, and a good actor. Hmmm....
It is true, a real actor Gollum would be quite different from the animated one. Perhaps it would not have worked out as convincingly on screen, we can only speculate. I do applaud the more-or-less realistic animation used to make Jackson's Gollum, I'm sure it was a tour de force of special effects techniques.
As others have suggested, perhaps my problems with the character were more due to script direction than to the animation (if they had just toned the antics down a bit, and no cutesy-Gollum for Pete's sake!). Thank you for making me rethink my opinions, I think I'll watch the movies and give animated Gollumn another chance.
P.S. here is Michael Therriault's Gollum.