I am torn on the subject. On the one hand I don't like BMI since it does not account for muscle mass. I gave myself a good body for my 40th birthday -- over a year of intense workouts and diet. At the end of the year I had the least body fat I'd had since college (wrestled intramurals in college, so I wasn't a fatty then). I was muscular to the point where my wife didn't want anymore, and according to BMI charts I was overweight with a BMI of 28. 4 years later and even though I've backed off the gym a bit I've still got much of the same muscle with a little more fat around the waist and my BMI is now 29. I don't snore and certainly don't have sleep apnea, this would be a ridiculous intrusion for me.
Then there is the flip side. One of my roomates in my crash pad sounds like he dies about every 30 seconds while he sleeps. Very fat, looks like shlt, and probably at the high end of obese to low end of extremely obese. He snores like a chain saw, and literally stops breathing every 30-40 seconds. It was scary listening to him. I wouldn't want this guy flying my family around, would you?
I honestly don't have a good answer -- something should be done but this feels like your typical stupid government program that has good intentions but goes about it the wrong way (TSA anybody?). We should do something about people with sleep apnea, but casting a massive net over droves of pilots feels like the wrong approach.