Nice, This is cool, pretty much what I had in mind with some cool additional features. It seems like you could just pass the template to bindModel, fire a change, and have it do the initial render and cut out _.template altogether.
Template markup is generally more complex than that and certainly more complex than your bindings. The ability for designers to edit and change the markup without having to look at code is a plus for using templates. Not to mention as a backbone convention it is expected so it makes things more portable.
