People are allergic to any "fork action" of bitcoin. That is why XT failed so miserably, I am not sure if that proposed BIP of yours is not conservative enough for bitcoin purists.
Also I doubt that any changes that will push bitcoin into even more anonymous and private state will ever happen, it will be quite opposite route imo.
It's not my BIP. I'm not suggesting any specific BIP. I'm suggesting a BIP that would enable sidechains. Because I think that without sidechains chances of bitcoin getting mainstream adoption would be much lower. Why I think so - see OP.