Apparently you have never attempted to backpack in the Grand Canyon.
Generally speaking, the GSMNP system isn't that bad... and like any system, it's only as good at the people utilizing it. After all, there ARE 'rouge' hikers out there... those that camp in GSMNP without a permit... and there's no amount of "rules" you can put in place there is going to accommodate all the stupid stuff people do.
And you'll notice a common theme to many of these "what if" questions... "hiker arrives at 10pm/late/etc".
The lesson to take from that is that you should try to plan your days so that there is little chance you will be arriving "late" to a shelter.
And for thru hikers and section hikers alike... arrive at shelters at a decent hour, come expecting the shelter to be full (i.e. have a back-up plan such as a tent), and simply practice common curtsy... and everything will work out fine.