It's very easy to structure a plan that would clearly pass constitutional muster - you just define a "qualified plan" as one that passes your metrics, and then say that only payments to qualified plans are tax deductible and only qualified plans are eligible for subscriber subsidies. So insurance companies are then free to set up non-qualified plans, but these would be uncompetitive.
So at the end of the day this legal stuff is a quibble about form rather than substance.