We already have that: `gcc -Wall -Wextra`, and a few more flags for specific things that some projects find too restrictive.
Only very few flags warn or disable the use of entire language features. Most are warnings against dangerous ways of using some of the features.
I think what we need is a way to selectively disable language features. Changing the behavior of existing features is a much more questionable thing to do in my view.
The big question is if it's possible to disable some features without affecting how other features must work. It failed miserably for exceptions, but exceptions are a cross cutting sort of concern.