How much easier was the civ3 editor really? You had to go in and edit those text files, or whatever they were, for most things. And frankly, a lot of typing into that limited format of the editor was dull and done no other way, with its own special rules half the time. In XML you can cut and pastepastepaste and search and replace.
Of course a lot of those flags were really powerful and convenient. Someone could maybe write an editor, and some have made attempts. If they put an editor into an expansion it would make for more people getting into modding, not faster modding by people who are already in it. Civ 4 is a more complex game, and modding it will simply take longer because of that, not because there is no editor. Also the more difficult graphics are an issue. I don't see why firaxis didn't use more accessible formats. A large ready to use pack of supplemental graphics and animations would help make up for it, and I might not cry. If they put an editor into an expansion it should also be better than the civ 3 editor, not just comparable, to take advantage of experience. Basically something that sugar coats tasks for you as you change things (presenting things as what they are and what they do rather than the xml tag formats and sometimes unclear names), and also prompts you to fix conflicts in other files, so that say when you eliminate a tech it prompts you to fix all references to it in other files, such as units and buildings. The task of changing files is just putting together text, it shouldn't be hard for someone to program, but the task of finding conflicts would be harder, though something already does something like it when it tells you where the conflicts are as you start up a mod.
It would be nice if the XML had come with documentation explaining what things are and what they do and so forth. I got a book about XML but I can read about how schema are done all day and it doesn't tell me the dynamics of civ's XML structure. Sure, there's some value to learning by trial and error and guesswork from names, largely that stuff learned this way is learned well, but really it would save a lot of time to just have a guide, so that for instance I don't have to post a plea for someone to tell me where I can add new Promotions. I'm sure the same sort of thing is needed for the python. A comprehensive reference, documentation you know. Yeah, there are the wikis and tutorials but they are hit and miss.
Also a set of blank XML files would be nice, because I am wasting inordinate time deleting stuff I don't want in a way that doesn't kaput everything else. What I mean is a mod with minimal everything, so that anything that's in it you put in it. One building that has no characteristics of any kind, one unit the same, one promotion, one terrain feature and so on. But I'm making that stuff for myself as I go.