I read "drop-in" as dropped in to new code. Certainly this could never be dropped in transparently at an OS or processor level. As long as the change is opt-in,

I read "drop-in" as dropped in to new code. Certainly this could never be dropped in transparently at an OS or processor level. As long as the change is opt-in, neither of the things you mention are problems. I think a new world where programmers don't have to be aware of negative zeros, etc, would be appealing to a lot of people.