Hillary's plan unconstitutional? Yea, that's technically correct correct, but meaningless from a practical standpoint (so is Social Security). That horse left the barn door long ago.
There are many flaws in Hillary's plan (though it is far better than her first effort.)
If the Republican candidate can put out a credible free market alternative, that would be good - we should be arguing in favor of that. Should Hillary get elected, we need to work with her to work out a compromise that will avoid the worst parts of her plan.
The most important thing is to change the tax deductibility of individual purchased insurance to put it on a level playing field with employer based insurance, AND to keep HSA's in place. The latter are already rapidly expanding, and beginning to gain a constituance among some Democrat voters as well a Republican. Once these are well enough established, a further move towards nationalized single-payer health care will be difficult if not impossible.
OTOH, if we approach Hillary's plan with the attitude of "just say no" - no discussion, no proposaing of the alternatives, no nothing - than we are likely both to get a Hillary victory and get her plan, with all the negatives, rammed right down our throats.
MWL