Frankly, SS is a joke. It won't work to try and get rid of it half way. Like others have commented, it's a pyramid scheme. Allowing all the people who stand to make more by themself to pull out of SS won't work.
Ideally, we should be able to do whatever we want with our retirement money. Include waste it. Anyone can take care of themself if they try. I heard a great story on the radio the other day about a washerwoman in the South somewhere who washed laundry for 50 cents a load all her life. She put a little money in a savings accounts every week. One day she checked and it was worth $250,000!!! It was so much she gave $150,000 to endow a scholarship at a college because she didn't need it all. Of course, the fact that she didn't "need" that $150,000 indicates she was a frugal and financially smart woman.
Realistically, there is no way that will happen. If anyone so much as SUGGESTED getting rid of SS all the stories of poor elderly people struggling to make ends meet will be trotted out. Overlooking the fact that if they could have invested all the money they paid into SS they would be better off. (W/ the exception of people who got in really early and have gotten a lot out after paying very little in.)
Personally, I think the only hope is to mandate personal accounts. Continue paying SS to anyone older than a cut off age. Maybe as young as 18. Because everyone who's every put money into it will want their share. And then start mandating a savings account or conservative bonds/stock portfolio or what have you for everyone else. And require they put what ever percent goes to SS now into that account. Then, in fifty years, everyone would be financing their OWN retirement, they would actually have a real return on their investment, and they would have an asset to pass on to their heirs or charity.
The cost would be murderous while the government still had to pay SS to everyone w/o money coming in. But trying to keep this pyramid scheme propped up is a bad idea and it's only going to get worse.