Should Southwest Airlines Propose a Jumbo-bum Surcharge?

On our  flight from Portland to Chicago Midway we were boarding with only middle seats still available. We needed to sit towards the front so that we could later rush to our connecting flight to Manchester, N. H. with only minutes to spare. On the first seat available the people on both sides (aisle and window) were spilling over and under the armrests. The rotund lady sitting by the window had her large purse in the seat as if to say it was already claimed territory.  When Janeil asked for the seat the lady then mentioned that there were seats available in the back of the plane.

Janeil spent the whole 5 hours in the seat with her arms locked to her sides because the armrests were occupied. If she had been as clever as Steve Martin in the film Roxanne there are probably 20 retorts  she could have fired at her. Such as, "Did you pay for two seats?"

If people have posterior dimensions that take more than one seat width shouldn't they be surcharged just like excess baggage? Most airlines have a gauge to check the carry-on luggage dimensions. In a like manner the airlines could install a seat at the boarding area that has an alarm indicating when the flab limit has been exceeded. The surcharge would only be required when only middle seats need to be used.

Postscript, we made our connecting flight even though I forgot my coat in the overhead storage bin and had to elbow my way through the departing passengers to retrieve it.