That is one of My problem. I imagine that this is where we could add XML modification and packages of modifications.
But the problem with modding is that it seems to only add stuff but never gives you the option to remove/replace stuff.
If I design an XML file that changes the effect of city level up, it will be added to the files supplied by the basic game, but it will not replace the content of the basic game.
So my question is, is there a way to exlude XML content from the XML compilation to change some rules from the basic game. A way to say, if you play that mod, do not use file X and Y during the XML compilation.