The insurmountable quandary facing Republicans is the undeniable need for a mandate to carry a basic minimum of insurance for any system to work. The first demographic to opt out of coverage for cost is the exact demo that the pool would rely on to hold down average expenditures, the young and healthy. Without their participation in the pool, the averages skyrocket, but they are not immune to the need for coverage, especially if they have a family.
Even given their relatively low cost in a pool they can add sufficient unpaid billing to the system (they also tend to be the lowest earners) to send costs to insured patients through the roof as their billing is folded back into the numbers needed to keep provider systems functional. A $15 per hour worker at 30 hrs per week isn’t going to voluntarily commit to even half of premium cost deductions from their pay if no mechanism is in place to force them to do so, but they will utilize the ER for their care if necessary, as we all would.
This cost shifting is one of the big drivers of cost increases for insurance and isn’t going to be easily solved without significant subsidies. Also, mandating coverage isn’t the panacea one might think either, as premium costs can easily push one’s already borderline income below qualification levels for other public assistance which will simply provide deceptive successes in narrow classifications while costing more elsewhere.