I think we need a new feature, to build in city-states. I am thinking Portuguese for example, we installed "Padrão" in city states that were not ours, we installed "Feitoria" in city-states for the sake of trade in city states that were not ours. I didn't played enough to test unique tile improvements but what I read is that for instances you can build Colossal Heads in our territory, as a suzerain of La Venta. What I need is otherwise, if conditions are set, possibility to build in a city-state, in Portuguese case in coastal tiles. Both the city-state and the CIV must get advantage of that construction, one internal other by trade route, in case of Portuguese sea trade route. Thanks!