Personally, I would be willing to pay up to 300 just for the piece of mind that if I lose my job I'll still have care.
That is an exceptionally small number. Actual Medicare cost more than $800 per month in 2009. The typical Obamacare premium, which covers much less than Medicare, costs $359 per month just in subsidies. The actual insurance is even costlier, averaging $408 per month. And Obamacare is catastrophic insurance, with high deductibles.
It's worth noting that Hillary Clinton's health care/entitlements plan included a proposal to extend Medicare to those ages 55 and older (currently 65). So the concept is not totally ridiculous, just somewhat optimistic on price.
This is a common problem with health insurance. People don't realize how expensive it is and consistently expect that the price after subsidy by the employer or government is the real price. In actuality, the prices we see are almost always subsidized. Real prices would be much higher.
You might argue that the current subsidy would transfer. However, the problem is that the current subsidy is paid by the employer. You are taking the employer out of the system. Why would the employer subsidize a transaction of which they are not part? And if you lose your job, then you'd lose that subsidy anyway.
It's also worth noting that there currently is coverage if you lose your job. You can keep your insurance under COBRA. The problem is that you have to pay for the whole thing. No employer subsidy or volume discount. Many find it too expensive.
It might make more sense to add health insurance to unemployment. So if you lose your job, you have six months of paid coverage afterwards. That would be cheaper -- unemployment is a 6% tax for a 60% benefit. So just a 10% increase in the total premium for full coverage of health insurance. If you're willing to pay $100 over what you pay now, that should cover it easily.