Sadly, this is not easy... Right now, when sabotaging a city, CIV.EXE checks if the randomly selected building ID is not 0 (Palace), and then proceeds with destruction.
I can quite easily change this value to the building ID of City Walls, but then Palace would no longer be protected - in other words, diplomats would be able to destroy Palace (I know it sounds cool, but that's not the topic here ).
In order to keep Palace protected and also City Walls, I would need more room to insert more code checking for City Walls building ID, which I can't easily find at the moment... So -> not easy.
Hmm, ok thanks for checking that out though so i will still only use diplomats to establish embassies, investigate cities and in some cases bribe some units or steal some techs.. everything else seems overpowered. Would it be easy to change the "incite a revolt" function so that the price gets multiplied by 10 or to make it possible only if the city is in disorder already or if the size is not higher than 3 for example?