If he just took us back to Obama's first two years it would be a lot better than the shite-show we have now. Remember back when constitutional democracy was a thing?

He could gives us a repaired ACA and force all states to expand their Medicaid up to the bottom of ACA eligibility. (Or just replace Medicaid with ACA that goes all the way to zero income.)

He could give us a public option in all states, which would quickly replace all other plans because it would be 15% cheaper for the same thing. That gets us to MFA, except ACA plans actually tend to be better than Medicare. For example, my ACA-compliant Blue Cross plan had a drug cap at $2000. I pay over $6000 per year for drugs under Medicare Part D.