I understand what you are saying and there is a certain logic to it however, from what I have observed many people take a part time job at American Airlines with their primary motivation for doing so being insurance. PT with a goal of upgrading to FT would most likely take part in the insurance plan.
To tell the truth NYer I have mixed feelings on this subject. I understand the membership's goal of keeping insurance affordable, but I also question saddling someone with insurance cost when they may already have insurance from another source (full time job, spouse).
I ran into that when I hired into American Airlines. I already had insurance (better and cheaper) through my wife's employer. I was told I had to take American Airlines insurance as a condition of employment. Was that fair to me to force a higher cost plan on me as a condition of employment when I got no benefit from it and was already insured?
I think this is one of those issues where there really is no right answer.
I guess at the end of the day you have to ask yourself if the benefit you receive from forced participation justifies the burden you are placing on the individual.
For whatever it is worth I doubt you would see a max exodus of insurance participants from part time workers.