Ingress, Niantic's previous game, has a Missions mechanic very much like what you're describing (missions are player-created, even), and focused very heavily on

Ingress, Niantic's previous game, has a Missions mechanic very much like what you're describing (missions are player-created, even), and focused very heavily on global events tied to specific locations. So it would not be at all surprising if similar stuff found its way into P:Go.