Of the current operation's i'll list if i think there effect seem "fine" Intel should probbly also let you veiw what techs the empirehas researched.
|Gather intel is fine it's purpose is to increase intel to do more complex operation and it fill that role.
Spark diplo incedent while not particuarly powerful can theoretically turn a vote in you favour by dropping their diplo weight by 10%, the effectiveness of this operation get's weaker v.s empires with alot of envoys but that makes sense, if you have a robust diplomatic empire they could feasibly sweep a diplomatic incedent under the rug.
Acquire assest & prepare sleeper cell's both have purposes and likely work fine.
Extort favours is fine it's gets you extra political weight, it's effectiveness is alot lower v.s ai since you can buy favours off them. Presumably it's intended that that the target empire know who did this operation against them since you would have to interact with the empire the extort the favours.
Extort favours could be expand upon by having the operation split into accquire senstive information, which would be a secret operation that would give the ability to do the exort favors operation in addition to force break trade deal, research agreement ect. Where the target is then given the option to do the require task or suffer some other penalty likely diplomatic although it could also be a penalty to stability, or happiness or production for 6 months.
Smear campaign has problems as is onyl ever going to be able to work between empire that were already teetering on the brink of hostility. Since if the negative oppions was higher enough the break up friends it would be quite annoying. My solution to change smear campaign would be that it now applies a modifier to the emipire in relation to everone else -150 oppinion and then also give them an situation where they need to conteract the smear campaign to activly reduce the negative opinion.
A more aggresive version of the smear campaign would be to be able to tag the empire for uncommited warcrime such as xenophage ect with them needing to complete a situation to remove the fake opinion modifer. The issue with this would be that -1000 xenophage would have to be insanely expensive for an opperation since it would delete all of their relations with every other emprie in the galaxy.
Steal technology is fine probably change it to gaining a flat ammout in the technology as opposed to a percentage as "generally smaller empires are going to be doing espionage so gainng a flat ammount of research towards the stolen tech is going to benift smaller more than large. Additionally maybe give the option to either target a specific tech or at least a specific science tree.
Sabotage starbase should likely actually take a starbase out of commissio with the caveat that a module should be buildable with the starbase to defend against such operations. The reasoning for this is that the ability to just switch a starbase off right before war decing someone is insanely powerful and being able to freely do it with not counter play might be to strong.
Weaken imperial authority probably needs to be alot stronger as in the current set up it's almost impossible to start a rebellion althogh this could likely be solved other ways by having everone in the galaxy not being in love with the emperor. Maybe give some more "evil" resolution for the emperor that reduce the oppion of other empires in the galaxy. Maybe have the ability to secretly undermine the imperiums authority with envoys with reduced effectiveness and the operation makes then more effective in addditon to current effects.
Target seditionist is kinda pointless since you could just kick the empire from the empirium and crush them.
Spark rebellion does what it says in the name, maybe you should be able to pretend a different empire was sparking the rebelion but thats about it.
For new operations something to reduce the loyalty of someone's vassals could be useful.
An operation that starts a war with another empire which gives and situation that can be completed to try and end the war early.
An operation that triggers the robot uprising with an empire.
An operation to start a slave rebellion within an empire.
An operation to set up a crime hub on a planet, this would synergise with criminal megacorp.
Technically there could be a force vassalise opperation but it might be a mulistep chain involving replacing the leader of the contry with one more sympathetic to being vassalised, building suport from general popilation ect.
Probably a good oppition for more brutal operation is the give the victim either a choice between to bad options, or give them a time consuming task to fix what ever problem was caused.
If there was a break mega structure operation is would likely need a massive cost and a empire wide lock out of more than 10 years, so only one emprie cant hit you with it every 10ish years. If it was less than ten years the repairing of the megastructure would need to not use a megastructure construction slot and likely also be alot cheaper than normally building the final stage, or it just takes less time to fix.