Interesting. It sounds like Mozilla is implementing something similar to Privacy Badger, which gives users control over which tracking sites are blocked and which aren’t. Thumbs up for Mozilla!
Now, if only they would remove useless features which rely on proprietary code, like Firefox Pocket. I have nothing against the idea of pocket, except that pocket is based on a non-free addon. If it were re-written with free code, I’d be more than happy to play with it.