Hm? When I read my books about Japanese history I find a lot of rivalry and competition between those two. There where bans, takeovers of shrines and temples and so on.
True: There was also blending. But this same blending of religions also has taken place in the West: Ostara is not a christian goddess ... And the mistletoe at christmas also does not have it's roots in christian beliefs ...

This is a common prejudice: There has been mission and there have been wars in the history of buddhism. The truly can in no way be compared to the crusades. But they did exist.

True. But.
Is there something that has "created" the dao? Can there be an alternativ way besides the dao?
Can the truth of Buddha's enligthenment be relativised by different truths?
And so on ...

I think I understand what you hope and what you want your personal religion to be. But I also think that you idealize religious history.

I have come to think that this series is one of the true sources of both buddhism and chinese internal arts here in Europe ...

Maybe o sensei thought this way. But Ueshiba Morihei in 1924 set off to conquer a shambala.
As far as I know it was not as a soldier at war that he experienced hand-to-hand combat. But it was during this religious endeavor?