This way you can turn any wireless capable  machine into a small community network.
> great use case I've seen are college campuses where thousands of students connect to the same WiFi,
This is indeed a great use case. Right now you're only thinking about chat but its got more applications like semi-remote teaching,tests ,role calls etc. But (I think) its far easier to realize it if you work at the network level rather than at the app level.
Best of luck!!!!
 router, raspberry pi, laptop, your phone