I don't like the Espionate point system either, it has always felt contrived and frankly a bit of a lazy solution just having a linear meter.
It would make more sense to increase incentives to spend production points towards espionage buildings or spies. That itself is a cost, it doesn't require a separate meter. I'm not a big fan of pointless derivatives (like espionge = gold essentially), why not just use gold?
Also the spectrum of what spies can do feels a bit too big. I'd rather the options what to do with spies be more limited, but crucial, so using them feels more strategic and less like, well, just sending a unit back and forth doing irritating shenanigans.
The city revolt thing for example is cool, because it's a legit alternative to siege.