Feature request: View-type for numbers

Hi there,
is there any plan to have a "view" type for numbers? (I.e. something like what `std::string_view` is to `std::string`)?

The usecase we had in mind would be a type "views" into the internals of a boost multiprecision number stored in some user defined backend storage, and is primarily used for the purpose of abstracting away the allocator on the backend-frontend interface boundary (like `std::basic_string_view` can do for `std::basic_string`). I know, that is potentially quite a niche usecase.

So, basically 3 questions:
1. Like I asked on top: Is there already a plan to implement something like this?
2. If there isn't any plan: Would you accept a contribution?
3. If you do accept contributions: Do you foresee any major blockers that would prevent the implementation of that feature?