Create a new single payer healthcare system that is completely separate from anything existing now. Don't attempt to incorporate any existing insurance, regulations, medical records, etc. Allow the new system to ignore any existing drug patents. Get a few brand-new hospitals, a few hundred doctors fresh out of med school/residency, and tens of thousands of people using it - probably do this in a single city, a la Google Fiber. Spend a couple years working out the kinks.
Once that is done, migrate everyone to the new system over the course of a decade or so. Any existing hospitals, doctors, and patients are free to stick with the existing system, but I suspect they'll learn to regret that decision.
There are no technical or medical roadblocks to this that I can see. The only obstacles are political and legal, which can be overcome in one or two election cycles.