My plan is simple, which is why it will never be adopted. It's also by a person who understand the whole issue as a regular person, which is why it probably wouldn't work.
1) Allow anyone to buy into Medicare. Set prices based on costs, and use the clout of Medicare to keep costs reasonable (but not artificially low). Do not force anyone into Medicare, but make it a choice for everyone.
2) Don't force everyone to buy insurance. With one caveat. If you are able to afford insurance but choose not to buy it, you must pay for any and all health care you need by yourself. So if you refuse to buy catastrophic insurance (even though you can afford it) because you think you are invincible, then you darn well better be invincible. If you go into debt to pay off health care bills after you refused health care insurance you could afford, tough luck.
3) Pass a law that if a person dies due to insurance companies refusing coverage (and this needs to be well documented by more than one doctor, not based on a single opinion) then the insurance company is fined $1,000,000,000 with the majority of that going to the survivors. A petty sum for a priceless life, but maybe after paying a few billion for negligence, insurance companies won't deny critical coverage any more. As an alternative, I would favor murder charges against the person/people who made the decision to deny coverage.
I can see lots of flaw with my plan, but I bet any politician worth their salt could fix the loopholes and make it work. The crucial part of my plan is point 1, I could give up 2 & 3 if I had to.
The key is allowing people to have a choice between a single-payer system (Medicare) and private insurance. People will vote with their feet, and move from Medicare if it is crappy, or to Medicare if private insurance is crappy.
Right now, most people have the choice between an over-priced private insurance that will drop them like a hot potato if they actually get sick and... an over-priced private insurance that will deny them coverage based on loopholes and fine print if they get sick.