“Missions are specific initiatives aimed at achieving one of the Intents. They are tightly scoped and can be accomplished start-to-finish in less than 12 months.”
They are team agnostic. You can find an explanation here: Missions v2: Season 5
You can suggest event missions, but I would recommend it to be geographically agnostic and more general too. There are a few examples for hackathons here: 🏹 Mission Requests - Optimism Collective