That's a nice idea, also you could implement another checkbox: "Notify after connecting to this network". Well, you can just implement a checkbox for enabling/disabling /etc/network/if-*.d/*

And I've got a feature request: ability of assigning priority by ESSID (not by gconf UUID) - it will allow setting priority for free mobile providers APs.

Actually I imagined myself automatically receiving a notification about reaching free wifi area on a long walk through the city