Mod or MCCC setting to force couples to move out when they get married?

You don't even need a mod. In the manage world screen, if you click on manage household, you can easily split sims into separate households. All you do is click on the "create a new household" option instead of merging them with another household. They won't be in a world, but it's very easy to move them into a house once you create the household, and you can do it all without leaving the manage world's screen.

https://i.imgur.com/qJwuJ0o.png