I think Diplomacy Screen could be tweaked to display more information. For example:
What do you think?
I don't know if something like this is already modded or can be modded easily.
I attached an image as an example:
- if you already own the luxury a City State has nearby, display it in another color.
- if a city state have a luxury or strategic resource nearby, but the tile having the resource is not improved or the City State doesn't have the technology to work the strategic resource, put a (0) number in the quantity of the resource.
- if you have a luxury that a foreign civ doesn't have, show it in the Diplomacy Screen so you can see at a glance you can trade it.
What do you think?
I don't know if something like this is already modded or can be modded easily.
I attached an image as an example: