Hopefully politicians will not attack doctors and see that it is actually insurance companies causing the problems. As for your points above:
1) I understand this example, but I don't think it is the same as medicine. Teaching is a 4-6 year degree and teachers are guaranteed regular work hours, every holiday with their families, and the entire summer off. HUGE perks there. I still think they probably don't get paid quite as much as they should, but I also think people forget all the vacation time when they see the average teacher salary.
2) True that tons of qualified students aren't accepted to med school, but their minds are no different than the ones who are. If salaries were cut, I'm thinking just as many of them would withdraw their applications.
3) Definitely, any cause/effect will be delayed. A generation will try it, but when the norm becomes the inability to pay off loans and doctors become very bitter, many of the shadowing pre-meds will start to rethink their career choices (I was pushed to reconsider medicine as a career when a couple physicians I know were forced to relocate or close part of their practice (OB) because they could no longer handle the cost of ridiculously expensive malpractice insurance). Perhaps, if this situation arises, America will see an increase in foreign med students who don't mind working hard for average pay, given the chance to live in America.
My hope is that when politicians begin to design a national program, they include doctors in the discussions. Medicine is about patient/doctor. Universal healthcare needs to keep both parties happy. If someone needs to get screwed, it should be insurance companies.