So roll Medicare, Medicaid, VA hospitals, and all private insurance into a single payer system administered by the federal government (or a one time bid to corporate America). Handle the buyouts of the private portions via a stock purchase on a given day's price of the health insurance portion of every insurance company, their backing assets, liabilities - the whole works. Also reform the tort system.
Establish two or three tiers of benefit plans. Everybody chooses one regardless of age and pays its premium. Parents pay for minors. You can switch to a higher level of service with restrictions to prevent picking a higher level when you get sick. After you move up, you don't get to move back for another longer fixed period. The young aren't disadvantaged by having to pay for the same level of care seniors might need. But by the same token, there are just two or three levels - each with higher amounts covered and more procedures covered as you go up, so if you want to have platinum level care when young in case something goes terribly wrong, you can pay for it. Provide coverage for catastrophic illnesses at all levels so if you are a rare person who gets some horrible disease, you're covered.
Employers are completely eliminated from having to deal with health insurance, regardless of size for anyone (current or former or retired employees). They should be required to pass the savings along in the form of higher wages as part of the benefit of dropping the responsibility.
One payer. Medical providers win since there's just one entity to deal with and because based on a standard plan they know what is covered. Since everyone in the country is covered (legal or illegal) since everyone pays, there are no more uninsured people to deal with. All costs not covered by your plan are out of pocket so there's an incentive to join up. Since everyone is covered the premiums should be low enough to afford.
Provide an insurance card / day rate for emergencies for any person travelling to the US from a foreign country. This wouldn't cover treatments for pre-existing conditions, for example, but would cover you if you broke your leg while here if not covered by your home policy.
You can go to any provider anyplace in the country for any service if available. Everyone won't be able to get an appointment at Mayo, but if willing to wait everyone could be treated anywhere. On vacation? No problem. Just moved for a new job? No problem. Figure out a national price for all medical services and drugs and allow adjustments for cost of living in particular areas for what is reimbursed to the medical community. Actually publish it so people will know what to expect out of pocket for any procedure. With the ability for any person to go anywhere, there's an incentive for providers to keep their costs down as well.
Each year, the amount paid into the plan by everyone is compared to what is spent by the plan. If less was spent than came in, the premiums go down for that class for the next year. This gives people an incentive to make healthy choices - not a big incentive, but something. If more was spent than came in, the premiums go up for that class for the next year.
Defense is a required Constitutional expense. Privatize Social Security.