If not done properly, anything code-related can result in bloated and inefficient code. I fail to see how introducing Javascript code that requires DOM manipula

If not done properly, anything code-related can result in bloated and inefficient code. I fail to see how introducing Javascript code that requires DOM manipulation is more efficient than a properly built style sheet. Injecting styles inline to elements is an even more inefficient way of doing things, you're likely to cause repaints all over the place during initial rendering. As I said elsewhere, if this were a system done on the back-end (or even in something like Grunt) so that it was part of a compiling process then it would have merit. But from what I'm seeing this appears to run only on the client side which I feel is a bad idea.