As Sakura points out, there are many shades of gray between a united clan and a completely separated clan and this was the solution we went with. I just went through the alpha subforum and me and the alpha researchers had a long discussion there (well, actually I mostly listened to those wiser than me) on how to deal with Takeda. So we didn't end up with this situation because we didn't bother looking up the facts, but because we made a different interpretation of the situation. It was also mentioned that since the two daimyos are so far away from each other, it would be easy for one of them to break away.