Spies can be very useful in S1914 but aren't very realistic. I think they need to be completely overhauled/redesigned. A shortlist of the changes I think are needed:
1. Experience Gain: A ubiquitous 50% success rate is kind of dumb/lazy. Spies should be able to improve and gain experience and have a success chance based on this (and other factors as mentioned here).
2. Country-level Deployment: Spies should not be deployed at the province level; they should be deployed by country.
3. Update Available Spy Actions: Once deployed spies should have a list of available actions such as:
- building a spy network (this would serve to improve spy success chances in general in this nation)
- monitoring communications/diplomacy
- sabotaging infrastructure in certain provinces (this is already doable)
- revealing armies (number of revealed armies should be based on success chance and skill of the spy)
- counter-espionage in own and in allied nations. This way you could assist your allied with espionage
- Disrupt unit orders. Assign your spy to disrupt/change the orders your enemy is giving to their troops
- create disinformation: you should be able to have your spies feed disinformation to foreign spies
- Assassinate foreign leaders: this is part of another change I want that adds in faction characters such as army commanders, governors, government ministers, etc. but that's for another post.
- Recruit foreign officials (again dependent on adding in characters to the game)
4. Make spies named characters with stats and traits (part of my recommendation to add in a variety of characters to the game.