I'd like to know who is going to pay for current retirees if I'm putting my money into my own private account.
Well by pointing out that our system is so inefficient that you can get away with redirecting a portion of payroll taxes for a net positive result. So you can lower future liability while dealing with current retirees separately.
In regards to current to current retirees that may include means testing the highest wealth people currently, cutting elsewhere in the budget, or if it was a part of a deal I have no problem agreeing to a small tax increase elsewhere to fund the shortfall.
You think a "small" tax increase would fund the shortfall? Check out how much SS costs.
