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.

They can be necessary for reasons other than CSS. Trying to do most of them, including CSS, without the usage of classes and ids is just a strange notion.

There are several different ways to handle CSS and each has their own pros and cons. But I'm assuming you're talking inline styles on the HTML elements directly? If so, while useful and I do it myself often, it is not optimum. If you're talking about injecting the styles on or before page load for that particular view, of course you can; but that doesn't mean anything different than what I've been saying at all. In the end it is still CSS and if it doesn't done properly in the beginning it will eventually cause problems.

I agree, but that's tomorrow and in the end that only replaces classnames and ids with something else which will serve pretty much the same purpose. You have to have identifiers of some type, today it is classnames and ids; tomorrow it will be something else.