Bloating the core with this nonsense is sad. If I had my way, I would want the entire "Customizer" code base to be a spun off into plugin itself not unlike JetPack. Distribute with WP like "Helly Dolly", people can deactivate / delete if they like. Then you're free to add what goofy features you like without much opposition. Developers that want to ensure it's installed / activated can use something like TGM Plugin Activation the way they already do. Just my two cents. ;-)