I just got an idea on how the mod can be made more realistic. I'm not sure it can be modded however.
One of the issues that breaks realism considerably is the compensation in gold one gets for failing to build a world wonder first. I actually abuse it very often for getting gold from hammers when I have the resources that boost the wonder construction rate. Where does this gold come from after a nation invests itself in expensive construction and expands resources on it? A way better compensation would be the ability to complete the construction, but get a second-rate wonder as a national wonder with much reduced/eliminated culture and GPP bonus and limited other benefits. In the case of the Great Wall, for example, this would mean no culture and GP points and only 50% bonus to GG points gain within cultural borders. I'm not sure, however, if there would be any way to prevent players from building wonders for 1 turn and relegating them to the bottom of the queue just to guarantee the ability to construct the second-rate wonder this way. One can go further and make all great wonders available as second-rate national wonders for everyone after they are completed, but this would result in a truly big number of national wonders.