The American Academy of Actuaries has many concerns about Idaho's plan to start selling insurance plans that don't comply with the Affordable Care Act. There's the whole part where federal government supersedes and that it's illegal, sure, but there's also the mess it will cause for the individual insurance market. They are not fans.
The nub of their argument:
Although offering state-based plans that can avoid ACA issue, rating, and benefit rules could provide lower-cost health insurance options to many Idaho residents, such options would lead to a deterioration of the state's ACA market. As a result, ACA premiums would increase, and options for individuals with pre-existing conditions would narrow.
For the sicker people who would stay on the ACA plans for the protections provided, premiums would increase, costs would increase, and companies would withdraw from the market. That's all bad. That's what Idaho is aiming for, perhaps being the guinea pig in a larger experiment to break the ACA, since Congress and Trump aren't going to be successful in doing that legislatively.