Pay by the Pound

I used to love going to a certain movie theater near where I grew up. Not because I loved the movies (which I do), but because they had one of those assorted bins of candy where you could pour it all in the bag and pay by the pound.

To this day, I love paying for things by the weight.. You know exactly what you are getting. If you want more, you pay more. You want less, you pay less.
While this is very predominant in grocery stores, delis, and drug deals, I think it should apply to people. If you are completely blown out of proportion comparative to your height, you should have to pay an inconvenience fee.
For example, on the subway, a 260 lb. 5'4 woman should pay $4 for being twice as large as the average person (who, by the way, has steadily been increasing in weight for the past 30 years). This woman is taking up twice the space of an average person, why should they not pay for two people? The same thing with airline seats. How many times have you been stuck next to some huge, sweaty hunk of lard barely passable as a person and the flab from their arms is rolling over onto you and you have nowhere to escape to for the next 4 hours (more if you are stuck on the runway waiting for the 57 planes in front of you to take off).

Or maybe instead of each service, there could be a flat fee? Like a Fat Tax. Every year you go to the doctor, they evaluate your health, and you have to pay taxes based on how unhealthy you are. If you are healthy, you wind up getting more money back.
Not only would this bring in money by unhealthy/fat people having to pay, by encouraging them to live healthier lives they would also (in all likelihood) not have as many health issues as they would otherwise, which means lower medical bills and less required medicare/medicaid assistance.

This alone is enough for a presidential platform.