Most companies that offer healthcare insurance do so by taking the amount paid towards it each month from your check, as are taxes. If you're employer doesn't offer healthcare, but give you a stipend for it then you pay yourself. The same applies if nothing is offered, but you want to buy insurance yourself. You pay straight out of pocket.
Well, if Congress is going to require a public-style option, then do so this way. For those who already have health insurance, allow them to keep it as is their right to do so for choice. If there are people who WANT the government offered public option, they may enroll one of two ways: 1. If your employer offers healthcare, tell your employer you want to enroll in the public option instead. File the paper work and the cost each month will still be taken out of your check like taxes, only now it basically is more taxes just part being paid for healthcare. 2. Your employer does not offer healthcare and you usually choose to buy from the private market. You simply enroll in the public option and again have it taken from your taxes.
I know this sounds to "simple" to be an option, but that's the point. As I said, I do not support the above ideas overall, but I think it is the only fair way to do so if the public option is implemented. Nobody should be required to have healthcare in my view. This is a choice, not a mandate. It is your life to protect, so do so at your own will.