It’s already a tiered system ie dependents, retirees. Retired military would benefit because there would be more providers for them to choose from. It has a good reputation without the baggage that Medicaid has.

I don't know the specifics of Medicaid, but Medicare itself is actually very good if you get the right advantage plan or Medicare supplement along with it. They could move the age backward a bit at a time, like say starting at age 62, eventually moving it back to include all.