Basically, your saying that we should reduce benefits, because the vast majority of people now collect substantially more than they put in. The biggest problem with this is that the people who would be affected the most would be lower income earners. Higher income earners would not be affected because they have other retirement resources. In the end, those lower income earners would be in much worse shape which would create the need for government to find additional funding for these retirees, and that puts us right back to square one.
Actually, it would stop unintentional increases in SS. If you think about it, every time your life expectancy increases, the total you will receive from SS increases, and it's this unintentional increase that has gotten SS in trouble. Now we all know the only way to deal with the expected shortfall in SS is to either raise taxes or reduce benefits or raise the retirement age. I'm suggesting a mechanism that would automatically make the age/benefit adjustment without requiring continuing acts of Congress on a crisis basis.
If SS had originally been set up this way, it never would have gotten in trouble, but neither would it have been a very popular idea at the time because hardly anyone was expected to live long enough to collect very much then. How do you think it would have been received by the public if FDR had said, "Look, I've got this great idea. You'll pay taxes to fund a retirement benefit all through your working life, and then you'll retire and collect a small benefit for a few months before you die"? Would that have gotten him a third term?