I think you and I are talking past one another.
Currently, f(a[]) with declaration void f(int a[]) passes a pointer to the first element, with no additional overhead.
Under the proposal, f(a[]) with declaration void f(int a[]) passes a pointer to the first element, with no additional overhead.
Help me understand why "other people would care"? What is the negative impact on someone who would not use the a[..] functionality?
So, I go back to the idea that it seems unlikely this would ever be an official C change.