Enhanced Diplomacy
Right now your Sovereign is godlike in his intelligence gathering. You know exact stats of other factions, what tech level they are at, even their income rates! I propose as a way to make Diplomacy path more useful we add Intelligence related techs which would add spy type units and related structures to defend against spying. In addition your own intelligence of other factions would be minimal at best without use of said spies. This would reward people who take a stealthier/political approach win the game with superior information and information defense.
Extremly simple sample tech tree
Reconnaissance: Unlocks some of the scouting gear moved from Warfare Equipment Tech. Thereby slightly nerfing warfare tree to make diplomacy more desirable.
Intelligence Gathering: Unlocks spy backpack, which allows the unit spy abilities.
Surveillance : Unlocks some sort of defensive structure to lower chances of spy success, unlocks watchtower structure too perhaps!
Advanced Intelligence: unlocks advanced spy backpack (same as first but also allows spy to be hidden from sight, but cannot use weapons/armor), prohibitively expensive cost.
Homeland Defense: Unlocks advanced watchtower and superior anti spy structure. Maybe one of those one per faction buildings related to diplomacy
Sample Spy Actions
Spy must physically be adjacent to the following
[Spy on Unit]
Scout- You can now see what units are in that army
Go Undercover- Uses up spy, you can now see what units are in all their armies for 10-20 seasons
Poison Unit- Unit is now "Poisoned" (10% stat reduction for 5 turns)
Grand Theft Carriage- unit move points decreased by 1 for 5 turns
[Spy on City]
Sabotage- Chance to delay current construction
Intel- Chance to reveal information about the city such as buildings and income (updates your faction intel too!)
[Spy on Capital] (Capital gets some sort of additional spy protection bonus)
High Profile Spying- Chance to reveal a random aspect about the faction, such as exact adventure tech level, gold income, etc
Kidnapping- Chance to kidnap a heir (can later ransom them back)
Arcane Anarchy- Chance to delay arcane research
Tech Travesty- Chance to confuse researchers and increase time for current tech.
For balance and roleplay reasons the spy should always have a chance to get caught. I didn't add any tech/resources stealing powers in my sample examples as I feel it doesn't fit the flavor of the game as you can't even trade techs by diplomacy.
Other random thoughts as I come up with them
-Using traded away daughters to get some intel leaked to you from time to time.
