It sounds easy enough to disable a foreign palace from being built. Find the code that enables it in the first place and kill it. Possibly under leader traits. For the extra yields, that would be a bit touch. Marking a city as "elven" for the purpose of being able to build improvements... That's also tough. Could make it check for the "elven" worker promotion rather than being based on leader. Xenophobic elves rejecting foreign workers isn't too unusual. Or could make it an or check. For the other bits, you'd have to find pretty much every unique civilization ability and do a check, "was this city conquered? Andif new owner is tolerant? Then grant this bonus regardless of civilization." Something that would be nice is if the units's racial promotion was based on the culture makeup of the city. That is, if it's 20% dwarven, 80% human, any worker generated will have a 20% chance of being a dwarf. Added in with my cultural model (which I'll modmod in soon) and that would be pretty fun. Edit: Took a peek at the leader changes, it's in the xml for the yield bonus for malakim and desert. So I'd go to where terrain yield is done and the civ's yield bonus is added in and do an extra check: Is city conquered & is city owner tolerant? Then use max(original owner's formula) or (new owner's formula).