I actually tried coordinating an effort like this with my neighbors when I lived in an apartment complex. That effort very quickly died, for most neighbors not knowing much about their wifi other than that the box with blinking lights made the Internet go, and not a single stock firmware I encountered exposing a TX power setting anywhere in the configuration interface.

Hopefully someone with that much kit would be the kind enthusiast who'd be running firmware that allows you to turn TX power below 100%, but it could just as likely be someone who really likes being able to set their light bulb color from their iPhone.