See, your are only looking at the mandatory aspects of the plan. Even now, more than 80% of folks have, through there own sense of personal responsibility or by way of employment, have elective health insurance. To say that mandatory insurance will cause these people to choose a poorer plan possibly, is nonsense. Instead of calling it mandatory insurance, call it, mandatory participation. Under Mitt's plan apparently, one, if they have any means, must participate in the society of those financially and socially responsible.
Not at all. You're assuming that insurance companies remain static no matter what happens. The reality, however, is that they know now that they have to compete for people who would otherwise go uninsured. Take away that possibility, and they won't have to work as hard to make people want to be insured.
On top of that, if the state makes insurance (or "participation", whatever difference that terminology makes) mandatory, then that will necessarily reduce further opportunities for new insurance companies to start up and compete with the existing ones, because the state will start to impose more stringent "standards" regarding who can and can not be an insurance company. What that translates to is that only people with political connections will be able to start a company. That's what happens when mandatory auto insurance is imposed. You get a state-protected cartel.