So I was doing play-testing of some custom ruleset features I'm working on, adding to the civ2civ3 ruleset. I noticed, what seemed weird to me, that the AI got the Great Wall wonder very quickly, in what I thought was suspiciously few turns between when I saw the message "Aztecs have started building Great Wall" and seeing message "Aztecs have built Great Wall". This was still in the early game, I have 6 techs, researching Currency. Too early for anyone to have Trade and use caravans to help build wonders, which I don't think the AI's are smart enough to do anyway. I gave up the game because I wanted to tweek my ruleset customization, but I was curious about the wonder thing so I found a saved game from a few turns earlier and loaded it. Then used edit mode to plant a spy next to that Aztec city and investigated the city - wow! It was size 2, had low food surplus and high shield production and was building a settler. Which it couldn't do because it was size 2 and in civ2civ3 ruleset settlers cost 2 population, which results in a limbo state where the shields just keep accumulating - it had 117 shields stored. A case could be made that this is a bug in the AI, it shouldn't be trying to build a settler at size 2. But it's also an exploit that allows storing up shields for a long time and then using them for a wonder when it finally becomes available. Human players could do the same exploit - when the wonder becomes available change the production from settler to warrior with no loss of stored shields, then start the wonder next turn with a head start.
Unclear if anything can or should be done about this.