Based on my research, I'm not aware of any country (Canada being an example) that doesn't have a massive "2nd Coverage" market - because the bare coverage is comparitaively dog shit with insane wait times.
Feel free to correct me if wrong there - i can't speak behalf on a country I haven't lived in. The basic message was that if you're in the middle to upper class (basically anyone on AT), just about everyone had 2nd coverage.
So to the point of budget replacing other coverages, how do you defend that against everyone needing 2nd coverage?
IIRC "2nd coverage" as you call it is supplemental insurance for things the government system doesn't cover. Exactly the same as having supplemental insurance as a retiree to cover whatever Medicare does not. Those kinds of plans generally cost like $100 a month, depending on what you want covered. I doubt many young healthy people buy it. In Canada, I don't think the government system covers, for example, at home care.
My issue with the current MFA proposal is that it's replacing $33 trillion a year in healthcare costs with $32 trillion in government insurance and, to that, I'm sure more will be added for the supplemental insurance. Yet in Canada, they pay half of what we do, meaning this isn't a problem with the idea of it. It sounds more like a problem with the specific way they structured it. But this is campaign policy, not real policy. In reality, we're not going to implement any UHC program with that price tag.
So I would agree the program cost is too high in its present form. But that is no excuse for ignoring the other half of the equation and just quoting the cost of the program. The media, BTW, has aided and abetted this. Over and over again they quote the Koch Brothers think tank's "$32 trillion" sticker shock number with no added analysis. The "liberal media" is helping to kill the idea before it even gets started.