After looking around a bit, I still don't seen any mods involving the addition of new villages. I was working on one that did add several villages to the game, however many life altering events later and I finally have got back to finishing the mod, though its not to share, I am sorry, I will share the code that results in getting more than one village to generate. One reason I wont share the mod is I base edited the code which is frowned upon and its for personal reasons I even finished. I have lost all original portions of the code from years ago and had to start from scratch and it was for my son, whom is no longer with me.
There was another mod at the time called Diversity, by Budd, and if you can find his code on github, it is overly complicated to do what I am about to show you. It is not my code so I can not show you the link. Also it requires more than one class to simply load several villages. In forge, during minecraft 1.6.4 and below, not sure about recent You can only replace the mapgen files, not really add to them if adding the same thing. So, I was looking for the simple solution that would result in doing just this. And it is as follows, minus the loading of the new MapGenVillage, thats up to you how you want to do this. Though once you add the code to load replace the MapGenVillage, this goes in the new class
Create Your New MapGenVillage and copy the original changing the following bits
You'll notice thats comes just before the boolean method isSizeable.....
change that to the start method from MapGenScattered Features and remove the code bits for generating the features to look like this
Now, where those bits were, you will replace it with this...
If you make those changes, and make sure the spawn array list at the top contains each biome represented at the start method. Using this will give you four villages total, and using the variance code for desert village you can change the same villages many times. However this will give you four distinct villages if you change the shape and style of each village structure. you can also add more than four, this just gets you started. Dont forget to resgister all the village pieces for each piece class. have fun Sorry for the messy code blocks, it wasn't like that when I was making the tread