They already have. Numerous private and state plans already kaput -- no funding and no budget after the first of the year. It would not even be legal to re-enact those plans. No going back now and no alternative (as you say) put forth by the Republicans.
The defunding should have occurred three years ago and on an ongoing basis since then.
Real answer...private clinics on a pay-as-you-can basis, with a minimum for a visit. The catch? Maybe if you've got a dread disease, the only care you'll get is a book about nutrition, healthy lifestyle, and exercise.
The fact is it's impossible to care for everyone with the most expensive treatments. If it is necessary to meet a need, cheaper alternatives will be discovered and used.