Eurekas / Inspirations from capturing a city and its infrastructure rather than having to build infrastructure.
This reminds me of an idea I had a while back in the Civ6 cycle, which I think would be really cool (if somewhat tricky to implement):
When you meet a new civ and they send you a delegation, the Leaders have dialogue lines we've all seen a million times now, like "I bring you the freshest Pecorino Romano," etc. Now, when you receive a delegation from Genghis Khan, he says "I am sending you gifts—surplus horses, a youth's bow, and
airag to fortify you. Drink up!"
This made me think, instead of, or in addition to, the 25G for accepting/sending a delegation, it'd be cool (and make a lot of sense) for civs/leaders to have an additional "gift" or set of gifts that come from meeting them. Like if, when Genghis Khan sent you a delegation, you actually received 20 horses and/or the eureka for horseback riding. For Magnificence Catherine, maybe a free copy of a unique luxury. For Mvemba a Nzinga, maybe a free Great Prophet Point per turn, etc.
I mention these ideas specifically because it'd be possible to tailor each civ/leader's "gift" towards something which would indirectly benefit the leader sending them. Genghis Khan wants his enemies to have cavalries that he can convert to his own. Magnificence Catherine wants her rivals to have enough luxuries that they can have spare ones to trade. Mvemba a Nzinga wants his neighbors to be founding religions to send to him.
But it also makes it more of a judgment call as to whether you send neighbors a delegation yourself, since the benefits to them might more greatly outweigh the benefits to yourself.
Anyway, just a thought I had which I think could add some cool flavor to the game.