You can't subsidize bad decisions. If you tell healthy people that you can buy insurance when you get sick at no significant penalty, that is exactly what they are going to do.
As for who is going to pay for the emergency room care, we're only talking 40 billion a year in unpaid hospital bills in total. This isn't a significant source of inflating healthcare cost. Charity needs to be a factor here, we don't need the federal government to take over the entire health system to fix things like this. If we guarantee people housing if they fail to purchase fire insurance and their house goes up in flame then nobody is going to buy fire insurance.
While I would love to support your assertion that "you can't subsidize bad decisions," it's just not realistic. My libertarian core would love that we could practice in such a way, but we can't because it some point, the government will be picking up the check because we have agreed that we are not going to allow people to starve and die in the streets.
As I mentioned earlier, what if charity doesn't cover the bill, or there is no charity? Who pays? The hospital just takes the loss? We can't exactly require providers to treat, and then expect them to do it for free, can we?
How do you define a bad decision? What about the 19 year old type 1 diabetic that is finally realizing the gravity of his condition after poorly controlling it for the past decade and now living with permanent health issues because of it? Too bad? Your 10 year old self made bad choices, deal with it? Blame the parents perhaps?
I agree with you (earlier in this thread) that health insurance is not really insurance, and that's a huge part of problem. The entire system is set up for failure, unless of course you're a large hospital system, pharmaceutical company, or medical device maker in which case you're making tons of money privatizing gains and socializing losses.