I don't see what the problem is. Getting screening for medical conditions through these new regulations might actually save your life. There's no way you're going to be healthy if you have a high BMI. You're out there driving thousands of pounds of truck. If you're not in good health, you are putting the public at risk. I think there are a lot of drivers out there who need to start taking better care of themselves. Maybe this will be an incentive for more drivers to get in shape!
As several others pointed out, one absolutely can be in good health with a BMI greater than the arbitrary cutoff. One can also be in apparent good health and drop dead without warning.
What I think will happen is just more churn: drivers will leave the industry, [voluntarily or not], and new bodies will replace them. And I doubt they'll be all that much healthier, or lower risk, either.
It appears to be a lucrative issue for medical providers, with exactly the opposite result for drivers forced to quit driving.