Feature Request: Minimize scope of member

The "move declaration closer to usage" quick fix has given me an idea
that I don't think I've seen implemented before:

How about a refactoring that will reduce the declared scope of a
member, based on its usage throughout the solution? Should be
straightforward to implement, and it would be a really handy cleanup
task.

You could even apply it at the project or solution level, and tighten
up your whole codebase at once.