I don't see how this is any different from what we have now. The burden of funding high risk patients will still be placed on the general population. Only difference being it's now in the form of taxes instead of mandatory coverage.
The top 5% of people incur 40% of the claims. Claims per member in high risk pools go the roof and ultimately end up crashing. These claims are normally rolled into the entire group if we're talking about a employer plan.
Shine a light on how expensive the high risk pool is and people eventually decide that it is "too" expensive. There is no group cohesion and it only affects a "few" so let it die.
That has been the case of every state sponsored pool and also the trusts I've seen that accept individuals with no underwriting. They always go belly up.
This will be straightened out as soon as the masses of those slightly above subsidy level start running out of options. They are feeling the squeeze now. I'm expecting ACA to hobble along for next year with at most 2 carriers but 0 to 1 in many areas. All who can will bail. Repubs will allow some underwriting but won't do much. More insureds will bail as will carriers. This will cause rates to go quickly much higher and 2019 will require a massive contentious revision.
That's of course IF there are any carriers in 2018. Carriers can be bribed - but it takes money.