Allow people to opt out of Medicare and not lose social security.
Give those that opt of of Medicare a voucher (in lieu of Medicare coverage) towards the purchase a private policy. To save money for the program, the voucher could be less than the cost of Medicare coverage.
Allow Medicare patients to see doctors (that accept Medicare) and engage in private contracting and negotiate prices.
Employer health and dental benefits do not cover physician care. A medical doctor cannot (with a few exceptions for non-essential procedures such as plastic surgery), charge a fee for services in a clinic or hospital. What you typically get is some level of prescription drugs, semi-private hospital room, non-emergency ambulance. Dentists and optometrists can still operate privately. A friend of mine just received notice of a specialist appointment for a serious (but not imminently life-threatening) condition after waiting 22 Months. 6 to12 month wait times are very common. This is what awaits Americans if you ever adopt “single payer” health care.