So there would be natives of the area and they would try to take back their lands? 
Eh, I'd prefer it if the Laguz were the natives, and when the Beorc came over they were pushed to a little corner of the land. Of course there would be Laguz that think that killing one another for the return of their land would be bad and that there are other ways. 

Maybe the two rival families/kingdoms have to work together in order to fight the (Laguz) threat or something? Maybe the heads of the kingdoms aren't right and they just want the Laguz out of the way? Idk.