Essentially, that's what we have today.
Obamacare requires insurance companies to accept anyone, regardless of existing conditions - a very good requirement, if it is managed.
Unfortunately, it wasn't. There is also no requirement to buy health insurance. Oh, there's an IRS penalty, but it's paltry compared to the cost of a policy.
Consequently, those least likely to get sick, younger people, just go without, and stay out of the pool. What you end up with is a high percentage of people needing expensive treatment in the pool.
Sort of like not having to buy car insurance until you had a wreck. Wouldn't that be great? Of course, the price would go through the roof... just like obamacare.
The only practical solution is to use the medicare model. Payroll deduction from everyone, so everyone pays into the pool. And the mechanism is already set up, just phase it in to younger groups. Why the repubs don't just do this is beyond me.
Why the dems didn't do it when they had both houses of congress is way beyond me. At one time, the democratic party was the party of the working class, those hit hardest by obamacare. Doesn't look like that's the case any more...