Once the empire is growing, and the monsters beguin extinction, the diplomacy takes a bigger role.
At this point of the game, to deal with the other factions should provide some more options to keep the challenge.
And of course, having an improved diplomatic system will benefit the whole game.

The research points trade system should receive a deep revisit, so why not thinking in adding something else?
Reading in different threads about diplomacy, I found some interesting ideas I wanted to show all together:

- To avoid abusing (players and AIs), maybe a cooldown (like 5, 10 or more turns) could be added on some (or all) of them.
- Treaties: Trade cities. I guess it would require a new screen or something to display tradable cities.
- Treaties: Trade units. Probably the same. Only trainable units at least (I don't want to think in a dragon's black market). Did anyone say champions too?
- Propose Pact: Open Borders. Feel free to walk across. Good for the relations.
- Propose Pact: Close Borders. It should decrease relations, then.
- Propose Pact: Break alliance. Can't wait 99 turns? Will it lead to war, or maybe not yet? Add a cooldow here too, 10 or 20 turns better than 99. And that could help in avoiding AI abuse.

- Propose Pact: Demand tribute. What are allies for? Single or regular payment for some turns. It shoud affect the relations too.
- Propose Pact: Offer tribute. Make an option for lasting XX turns, that should improve relations.
- Propose Pact: Resource treat. It would allow to trade 5% or 10% of a certain resource's production for some turns. A limited number of resource treaties should be necessary (maybe one per resource or per AI to see how it works?).

There are many other options, but I specially liked those ones. What do you think?

(Edit) Some more ideas:

- Sometimes AI offers pacts or treaties that you can only accept or reject. I think there should be an option allowing to modify the trading options.

- More to come?