>

That's why they have just started using the term "accessible" instead of handicapped.
I've had people "bang" on stall doors who aren't in wheelchairs, too. I think it's when they really really need to poop. >

Yeah, that feeling of "I'm seriously going to shit my pants" can make people do things they normally would not do. >

Yes, sometimes it even makes them shit their pants. >

That's one option, yes. 
Better than getting arrested. >

Why not do both? >

Disabled parking is reserved. Disabled stalls aren't. They are available,  not reserved.