I don't think you should restrict certain buildings after events. For example, i have a consulate level 4 and i can't upgrade it to make it look better because i declared independence. There's no way for me to get back into a commonwealth either as far as i know.
The reason for this is once you become independent you then are granted access to the capitols, it makes sense tbh that it’s all like that. Yes there is no way to get back under a commonwealth once independent and main reason for that if you unlock more buildings once your independent. The consulate is made purely as a pre-independent building and has far less value than the capitols. Reason being the capitols give higher trade cap, and more civics.
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