Yep, I have to say that between XML and what little I know about Python, this game's editor is a thousand times more flexible than that of Civ3 (I gave up modding that one, very quickly, out of sheer frustration). That is not to say it can't be improved, however. A more comprehensive giude to Python in Civ4 would be good, as would a few additional schema for XML (and/or the ability to mix and match schema) would be excellent!
Yours,
Aussie_Lurker.