Overly aggressive solution: custom preludes! Allow specifying a module that is implicitly glob imported the way that std::prelude::v1 is today.
Upsides: domain specific preludes.
Downsides: differing preludes.
Of course, it's not too difficult to make your own prelude module and import that at the top of every file, and that's explicit. So maybe the solution is to fix the #[no_implicit_prelude]/#[no_prelude] situation.