With the 1.2 update, I overhauled some levels and polished others to the best of my ability. That being said, I theoretically could have done much more, but I want to save my creative energy for another mod I'm working on. "Read More" for install instructions.
Note; I apparently forgot to upload some important folders in the release that has now been up for at least a month. I have updated the 1.2 release and it is fixed now. My mistake.
Create a new folder inside Barony or somewhere else easily accessible, and name it something like "Vanilla Barony". Copy the "sound", "music", "models", "maps", "lang", "images", and "data" folders, then paste them in to this new folder. Take the folders from the Demeine zip and extract them in to your base Barony folder, choosing "Yes" to merge and replace anything it asks.
Create another new folder named something like "Demeine", then when you want to switch back to regular Barony, take the current "sound", "music", "models", "maps", "lang", "images", and "data" folders and cut then paste them in to the newly created "Demeine" folder. Afterwards, take the "sound", "music", "models", "maps", "lang", "images", and "data" folders folders folders from your "Vanilla Barony" folder and put them back in to the base Barony folder.
Note that this mod is also available on the Steam Workshop, which makes this process unnecessary if you are using Steam, as you can switch freely between regular Barony and this mod through the Workshop menu.