I saw the reddit post about this and I'm glad I found this. I have some thoughts about this because I really like what you've done. A thought on surveyors to make them more useful, because the term "surveyor" and the image you have for them seems to me like they might have a scientific interest. What if antiquity sites had to be discovered by surveyors the way barbarian camps are invisible when outside of vision until you discover them? I think it's odd that discovering archaeology makes all the antiquity sites in the known world visible, so having a surveyor scout out the territory would be cool. Your manor reminded me of a history course I took in university where we discussed the rise of liberal arts in the renaissance and how people were encouraged to pursue many different avenues of study of the liberal and natural sciences, which to me would create a huge influx of great people.
Speaking of surveyors, you could have a large amount of exploration based gameplay if there was more they could "discover" by scouting out territory- think 19th century explorations of the heart of the African and south American rainforests- they could find hidden resources or possibly even hidden natural wonders. I wouldn't suggest touching existing natural wonders, but wonders like El Dorado or the fountain of youth would be excellent examples of natural wonders that could only be found by surveyors. Since we already have mythical natural wonders like those, you could add Shangri-la or something. I think it would be interesting to have something like that.
While we're on the topic, what happened to national banks [national reserve?]? There are national wonders for like everything else but not for banks.