Well, there are senate missions in this mod. Arnor isn't in this mod so that doesn't work.
As I said before, I think the hobbit units should spawn when a settlement in the Shire is under siege. Like the scripts in BC but just for Hobbit. I know they wouldn't go around conquering Middle-earth in the name of the Shire but they wouldn't let someone walk into their home and kick the shite out of them