There are two plans that, whether you agree with them or not, are at least published out there with enough detail to be worth discussing.
Bernie Sander's Medicare for all:
Medicare for All: Leaving No One Behind - Bernie Sanders
Ryan Newhofel's PHA's:
Sanders plan is the all-in Medicare for all. Private insurance could still exist, but everyone would still pay in to the new Medicare (so only the very wealthy could afford private insurance). His plan is somewhat vague on details -- he states that all co-insurance, deductibles, and donut holes would go away and medicare would pay for everything. As far as I can see in his plan, there would be no out of pocket costs for anyone. He states, with no plan how, that this would somehow cost less than current Medicare. I don't see how this is possible, other than large payment cuts.
Newhofel's plan is interesting. He advocates for forcing everyone to save a least $2000 per year in a PHA -- those who were poor would have it funded by the gvernment, those more wealthy would fund personally / employer sharing. Then, all first-dollar costs come from your PHA. He would then add a medicare-for-catastrophic-for-all on top of this -- if your PHA runs out of money or your costs are high enough, it kicks in. There's also a deductible that's also means tested. The idea with this plan is to allow patients to shop around -- instead of medicare setting prices, individual physicians could charge whatever they wanted (theoretically). Ultimately medicare would need to decide how much they pay for any event (for those that have medicare kick in), that will still drive prices it seems. He also wants to renegotiate how specialty care is paid for (i.e. he wants to decrease payment). He's very vague on how much this will all cost, guesses that a 7% medicare tax would pay for it (unclear if this would also pay for funding all the PHA's). But he does have a nice section where he shows you who the winners and losers are likely to fall, and it does allow for some market competition because people will be saving their own money to spend. And this plan is likely to make everyone unhappy -- which actually IMHO is a good sign.