If you had the ability to choose to invite someone to your Empire Federation (which will be extremely difficult as no one wants to give up their autonomy to an emperor), they don't automatically become your vassal. No need to worry about cohesion loss if unruly subjects can't propose laws. Emperor has an edict to disable law proposal changes.

For some reason, the cooldown timer doesn't seem to show up. Imperial (federation) Fleet has no hard cap. Need to be either Authoritarian or have the Feudal Society civic to form the federation. The project becomes available after the Empire has been formed for at least 50 years. This is irrespective of how many members are in the empire federation, so if there are only 2 members besides yourself, you cannot get the best reward. All AI empires will contribute to the project, but at least 3 subjects must contribute to get the best reward. Subjects will either willingly go along with the project, or be unenthusiastic participants depending on the Crown nation's relationship with the subject and the empire federation cohesion. They will gain -60 opinion towards the Crown nation, decaying at 2/year. Subjects who are unenthusiastic will resent their emperor for forcing them to contribute resources towards the project. Subjects who go along willingly will gain +10 opinion from the Crown nation, decaying at 2 / year.

Subjects can either willingly support the project, or unenthusiastically go along with the project. There are 2 different options subjects can pick. No subject of an empire federation can reject the project. It's the same as the hegemony federation project, with some differences.

Just like normal federations, the empire federation now has a project.

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