There's no question that firefighters are doing very honorable work.
But.....
Let's say the OP's story is featured in Inside UPS. All of the sudden, the company is officially endorsing second jobs that force part timers to take off at least 1/3 of their total work days. As long as the seconds jobs are of a public service nature. They're applauding what the OP is doing There's no going back.
So all of the sudden, thousands of part timers realize they can make extra dough AND not have to be in preload every 1 or 2 out of 3 days. They too become firefighters, policemen, government officials, etc. If you can attach "civic duty" to it, they're in. Hell, they would have done it years ago if they didn't have to show up at UPS every day. And UPS has to hire thousands more to fill in for them on those days. All because those part timers who are off are doing great work.
There can't be exceptions.