Forgive me if I'm wrong, but I feel like I've seen such "suggestions" in GHC errors before.

If so, does that mean there's some sort of mechanism in the compiler already in place for such error recognition? Like some simple pattern stuff?  If not, I think that it might not be bad to consider this stuff (misused packaged, changed semantics that create compiler errors), and to put something into place for future modifications. This could make it a lot easier to deal with unmaintained code.