When the happens does it screw up the AI's logic then, or does the game just go on?
To the extent that the AI might have some wrong thinking, it should be minor. It is entirely possible that there would be no problems at all, but I could not guarantee it.
The main thing with wonders, is whether you can build them or not, and in such a case, where you just gave multiple people the same wonder, it would still be the case that no one could build another. So that part should be working fine.
Now, if a city that has one gets razed, the right thing should happen, and I think it does, but that is the kind of problem you run into when you construct an invalid scenario.
I would say there is a 95% chance you are totally fine by placing more wonders than are valid, but there is still that 5% chance that something weird could happen.
Wonders are both tracked by how many are currently active and how many have ever been built. I am not sure to what extent that information is in the WB scenario file (there is definitely a lot of information lost going from a save game to a WB scenario file). If it is in the scenario file, you will want to be careful about adding and then removing wonders in worldbuilder, so this number gets out of sync, if you want the players to be able to build that wonder.
The best solution would be to mod the XML, but if you want to make a stand alone scenario, without its own XML, but using existing XML mod, I can see why this would not be an option.
I do not know what happens if you capture a city that has a 'world wonder' with a global effect (like the pentagon or statue of liberty) when you already possess such a wonder, but I suspect that you get a doubling of the effect (at least in some cases). The Three Gorges Dam would not have an doubling effect, because power is on or off, but having two pentagons might give you double the experience bonus.
This is the one purpose of each civ wonders, such as Wall Street or Oxford. These will be automatically destroyed when you capture an enemy city, so you do not get a double effect. If you are creating your own XML, then perhaps what you really want is a new each player wonder that has the same effect as an existing world wonder.
From the AI perspective, for the most part, the only consideration when looking at a city is whether it has active wonders, not much evaluation beyond that when picking a city target, so nothing should go wrong there.
Now if you want the AI to be smart enough to know it can raze a city with the Three Gorges Dam because it already has the bonus, it will likely see the city has an active wonder and probably keep the city.
-Iustus
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