What becomes of those who hover around elidgability limits?

One year you must buy and the next year your not elidgable to buy. People with irregular income are susceptable to this.

That will be a problem with insurance companies as well because new enrollees tend to be charged more. What happens if you must drop insurance to save your house or pay an ac or heating bill?

The whole problem is that there are people that need what money they do have for stuff they need on a daily basis. You might not have to use insurance for YEARS. Insurance is for a potential catastrophic event. Rent, utilities, clothing or a car to get to work or around so others don't have to be paid to do it for you are daily certainities. It's not certain you'll need an ER visit.