I came up with some ideas for Espionage that might be fun to add.

1: Stealing tech is great but sometimes you just do not want a tech to be researched by a race. I was thinking perhaps adding in ability for your spies to sabotage their research on techs. Depending on how high your Espionage is with them the more likely you are to delay or prevent them form making any headway with the tech. Once you start spending cash to use this you would be shown the tech tree for the race. Then you could click on a set number of techs you want to delay. An Alternate to this is just general sabotage where your spies try to delay any research potentially stopping all research for that race.
2: Counter Espionage so you can try to protect yourself from others stealing your tech or sabotaging it.

3: Production sabotage for over all lowering a races military and social production. Again the more you spend the more you lower there ability in both areas. It could be on a % scale and depending on how it balances out in the game could even go up to 100% killing a races ability to produce anything but that would probably require techs and very high and constant spending. This idea goes hand in hand with my first idea.
I was thinking these would require additional slide bars. For sabotage it should be under the current Espionage slide bar with perhaps a check box to toggle it from general to select. For counter Espionage the most logical would be with your domestic spending possibly tied with the military, social, research bars.
I think my ideas might ad in another dimension to the game making it seem more realistic perhaps each race would use them differently Evil races might be more willing to try and dominate others by shutting down there ability to produce anything or research anything. Neutral races might be less likely to shut a race production down but would do it when at war with the race. And good races might be more likely to try and protect themselves form spying and shut down evil races production levels