Employees at many large companies today already have the option of high-deductible insurance; scaling the new, as-yet-unimplemented guaranteed issue system "back" to require a mandate only for high-deductible insurance (and thus guaranteed issue only for high-deductible insurance) would not be a major change.

You are articulating the "moral hazard" concern with universal health insurance. I am recognizing moral hazard, and saying that it can be addressed in a universal system simply by setting the threshold that the system pays out at a higher number.