As you rightly point out Oxbridge largely ignore A level grades because whilst they are not considered worthless ( they expect the prospective student to reach them), they are don’t feel they can sift the students on the basis of them alone. As so many have the same grades.
You don’t bring in a new extra star. You make the decisions about grades more carefully. There was a time before Stars were even invented.
If you get an A and you deserved it you should get it.
The point of the grades is to identify the elite, the academically very able from the slightly less, still very good, and also to identify those that are not.
The system arguably is still not doing that.