Sorry Stardock I'm going to punch your baby in the face here for a bit. I was one of the earliest adopters of this game. I'll have to be honest I'm not enjoying it that much so far. I find it difficult to get some time into the game with my busy schedule. Then I play a 100 or so ish turns then I put it down. So I thought I'd explore a bit more to why.
Diplomancy feels very, shall we say Stardock-ish. It's there, it kinda works, but it's the same system that's been done for every other Stardock game. This is also a clone of the system that Master of Magic did. I think with this iteration it may be time to try and change up the formula a bit. I understand diplomancy is a very difficult system to develop but this system needs improvements. I will mention Civ 5 a lot here. I don't think that game has a perfect system but it does have some take aways.
Non Aggression Pacts ruin diplomancy, in my opinion. If you start next to Shaka, Monty or Atila in Civ 5 you know you probably are going to be a war filled game. To avoid war you are forced to give incentives to the enemy to not attack you. Gifts thats totally in their favor, but they can declare war anyways. Even if you are friendly with the AI they can still backstab you, never trust Ghandi. Non aggression pacts usually last too long and they are guaranteed peace. For the player they almost always can attack the AI on their terms. The only peace treaty in Civ 5 last 10 turns. Which is enough to get rest a bit but keeps war as a possibility at all times.
Say no to tech trading. It removes choice from the player because they can just buy all the techs they are missing. Leave that for espinoge later.
Colony trading - Why do games include this option. Check with your QA team. Does anyone use this feature other then to exploit the AI. Probably not. City trading should only happen either when the Attacker is Have it as a possibility to force broker a peace treaty but normal trading it should not be possible.
Ship Trading - Most games give the player the ability to choose what ships to trade and you usually get money for it. Not very exciting. It's also does not make much sense. Yes sir I'll buy the contents of your trash can for a nice sum of credits. Instead have the AI evaluate your ships and ask you to build ships for them for credits. Like a work oder or quest system. Also, trading away your standing Army doesn't make that much sense.
Luxuries - Civ5's luxury resources helped diplomancy. To properly expand your empire you needed lux resources.. These resources were limited in quantity and each player was usually had a monopoly on one type of resource. This forces everyone else into trading with them or limit their expansion.