Is there going to be an espionage system in the game and if so how would/should it work?

In Civ V, espionage is used primarily to steal technologies. In real life this didn't really happen until about the modern era, and espionage was used more for sabotage or military intelligence. In Civ 6 and EL they do a better job of it IMO, using spies to do things like assassinate a governor, recruit partisans, or siphon funds.

I feel like if espionage did more to evolve over time it could be more accurate - for instance, building an intelligence agency in the modern era could unlock new abilities, or reaching a new level of government (like republic or communism) could allow you to better spread dissent. I also feel like there should be an option to have proxy wars after the development of nukes, where if you fund a minor faction they will spawn new units to fight your enemies without triggering a nuclear armed conflict.