Thank you for your considered and encouraging response; I know Christianity and Aiki have been mentioned before so I was hoping at least some of what I said may add something new to the discussion. Thank you also for explaining your background, I found it very fascinating to see the journey, you yourself have been on.
Regarding your point about Shintoism and pantheism, pantheism is the belief that God is in nature/ the universe. Polytheism is the belief in many gods. I hesitate to use the word polytheism in relation to Eastern religions now as I know that even in Hinduism they would say they believe in one God - Brahman and all other gods are avatars of the one God. From what I have read about O'Sensei and his beliefs, they seem to indicate at least that his Shintoism was pantheistic. However, I am happy to be corrected if someone knows more on this.
For me, the Kingdom of God is to bring moral regeneration to the world, shine light on the truth of Jesus Christ as Lord and Saviour and bring about social justice. Within the Gospel of salvation from sin there is also a social gospel, especially in light of the 'second great commandment' to love thy neighbour as thyself. This is where I think the martial arts can enhance Christians' own walk with God and their ability to love others.