Some states had high risk pools before Obamacare and they worked fine. Maryland is an example. This is not a new concept.
35 states did have high risk pools but it's hard to say that they worked fine.
By design enrollment was kept low via high premiums and deductibles, long waiting lists in many states, and by not covering pre-existing conditions for the first 6-12 months of coverage.
Even then, the taxpayers ended up subsidizing the insured because all the pools operated at a deficit.
I'm not attacking the idea but there's a reason they needed the no-medical-underwriting provision in the ACA - high risk pools are expensive and unpopular, and the taxpayers end up paying anyway.
I do resent it when politicians like Tom Price try to blow smoke up everyone's butt by saying they'll create high-risk pools that don't cost the insured more in premiums without also saying that we'll pay for it via higher taxes.