Well, I have 3 llamas IRL, they're cute and fluffy. :3
Back to the actual suggestion!
Anyways, I thought it would be cool to have llamas in Minecraft. They'd be like sheep, where you could sheer them, and dye them. But also be like donkeys and mules where you could put chests on them! They'd be passive aggressive, like wolves, or pigmen, and they'd spit if you hit them. It would give you blindness for 10 seconds. :3 You wouldn't be able to ride them, as they are pack animals, but as I said, the CHESTS! WOO HOO! So you can take a lead and drag them around with you! Or, another option, you could make them be like dogs, where they could just stay there until you right click them again. And, when it starts to rain, or there is bad weather, they'd lay down. Like llamas to in real life!
They'd also have different coat patterns, like horses. :3
While llamas are definitely awesome, there wouldn't be much of a point to adding them into them game with this feature-set. There just isn't anything new, apart from the mob itself. As far as shearing them, there are sheep for that (as you said). Putting chests on them - donkeys (as you said). It's behavior is much like a wolf (as you said). Sure the blindness thing is there, but that's simply not enough to justify adding an entirely new mob into the game. Sorry, no support.