I can see the convenience of sort of importing implementations of traits into scope. One difficulty is that traits are used for core functionality, like dereferencing and comparison operators. It would be inconvenient to have to import the implementations to do these basic things and confusing if some commonly used types could have their basic behavior dramatically changed. Maybe that could be solved by choosing some traits that are more central and preventing them from being switched out by importation, so you couldn't for instance change what `==` does to a pair of `f64`s.