It looks like diplomacy is one of the last major areas left in C# development, but it's also one of the areas of Aurora that's traditionally been lacking, and one of the least discussed, which is why I'm making a new thread. The current state of diplomacy in Aurora is extremely simplistic. Basically, in VB6, if you can generate more diplomatic points than the enemy xenophobia threshold, you will eventually becoming allies, otherwise, total war is inevitable. I know Steve mentioned adding territorial claims and limited wars, which is a huge step forward, but there's a lot of room to expand.
Aurora is a great wargame, but historically, diplomacy has been pretty pointless, since fighting NPRs is fun, whereas allying with NPRs basically gets you some trade income and eventually tech sharing while the AI sends their fleets zigzagging dumbly around Sol in circles forever, slowing the game to a crawl, at least in my experience. I've been thinking about how to make diplomacy a worthwhile endeavor. I think it's critical that diplomacy be expanded because, for the first time, having several, or maybe even many, NPRs in a single game will actually be practical, and the games needs more interactions beyond shooting at each other in order to create a convincing populated universe.
My initial suggestions/ideas are:
Diplomatic relations between races are a sliding scale between, say, -100 and 100. The initial value is set based on the relative races xenophobia levels, and changes dynamically due to events. There is no hard cutoff of a negative value resulting in war, or a positive value alliance, instead the diplomatic relation score affects the probability of the AI accepting treaties or engaging in hostile actions. You can't guarantee peace by pumping out diplomacy points. Add some random variation, like "Xenoblob-UN relations take a sudden turn for the worse" - although maybe with some better flavor text - that directly affect the relation score.
Diplomacy points as generated by diplomacy modules, instead of directly affecting relations, are basically diplomatic currency. You can spend diplomacy points on actions to improve relations, or suggest treaties, or trade.
For territorial claims, have a tiered claim system. A more xenophobic race might demand complete exclusion of all aliens from their systems; a moderate race might be OK with another empire transiting their space as long as they maintain separation from their colonies, and a xenophilic race might even tolerate sharing system bodies.
Allow for mutually-beneficial trades between races that aren't necessarily allied. I think it makes more sense for civilizations to start trading first, and then become friends, not the other way around. It would be nice to be able to trade resources or even technology directly.
Make allies actually do things. It might be hard to make AI usefully support player fleets, but it appears the C# AI already has a priority tasking system for its forces - maybe, if allied with a player race, it can be made to temporarily assign surplus ships to player control. Likewise, there might be a "support allied forces" fleet order that places a fleet under the friendly AI's control while active, since the player might not have a complete enough picture to interoperate effectively.
Add some form of information sharing between friendly races. If I'm allied with an NPR that's getting wrecked by another NPR, they should inform me of the threat and ask for help.
Make the AI opportunistic. If I'm at war with an NPR, make them more likely to seek out another NPR as an ally; likewise, if a NPR I've been hostile with starts losing ground to another let them start making concessions. If the player is at war with an NPR, a third party might see it as an opportunity to attack either party. And so on.