One city per civ (One City Challenge for all)

[achiafo]

Hello. I'd like to request a mod, similar to one we had back in Civ V. What I'd like the mod to do, is give everyone one starting settler, but then make future settlers impossible to train. This makes for a very fun and interesting game where the only way to expand is through conquest, and makes playing tall viable again.

I don't think it would be incredibly difficult to create; even my own humble modding skills might one day suffice. But for those of you experienced modders out there, who may have some ideas and pointers on how to create such a mod, please help!