The opinion of the AG's office aside, I see nothing there that's complicated. The article bounces around making it SEEM complicated. But it isn't necessary to make testing before boarding a flight a legal requirement or a requirement at all. It should be entirely voluntary. Nobody HAS to be tested. But, if you're not, you must quarantine upon arrival. That's a powerful incentive to choose to be tested. Hawaii offers you two opportunities to be tested and avoid quarantine. Before you fly over, and upon arrival. In the former, you control timing, who does it, and you KNOW your outcome before you step on the plane. It would be pretty stupid to not take that opportunity. But if you choose not to, you get a second chance when you arrive. There would be voluntary testing available at the airport. You must quarantine until the results are in. If you are positive, 14-days. If negative, your quarantine ends. And, of course, if you choose not to be tested at either opportunity, 14-days.
That's not complex. It is entirely voluntary. It requires only modification to the public health orders, not the passage of any new laws. It doesn't require the airlines to do anything. But since the airlines have a strong economic incentive for people to feel safe going to Hawaii, they have every reason to help Hawaii carry out their system.