The purpose is simple, you would be an arrogant if you think you have God all figured out.
It seems like you are making a much stronger shot at doing this than I am. I am arguing that certain human made texts (the Bible and The Tao Te Ching) do not fit together well. In fact they contradict each other.
And even if you had God all figured out, you could not put it into words, you would need to create a new language with infinite number of words, such as nature has. Zarathustra, Jesus, Buddha, Mohammed, Lao-Tzu have done this, but they were only poets of the divine, they could never explain God to the fullest with the limitation of language.
How can we then be sure they would have agree on God. Their texts do not.
You argument is that the Bible "Yahweh" is active and the "Dao" is pasive; put those 2 together and you can get a glimpse of what God is. God is unification, not division.
1) I might get a thought about God, but I think you are confusing thinking about God and experiencing God.
2) Jesus made some very telling statements about division. Remember his sword speech. He also talked about people who are very unlikely to get into heaven, also setting up divisions. He judged specific individuals and specific activities. He encouraged us to divide ourselves from certain desires. Shall we toss Mohammed into the pot? Some heft divisions going in the Koran.
To me it sounds like you like the idea that these religions or these poetic visionaries really had the same ideas. But they don't. They say different things, they teach us different ways to come to heaven, they teach us different ways to relate to each other - just ideas on killing split that group up, they have rather different ideas about women, who to hang out with and even whether division is a good thing or not.
You state 'God is unification, not division'
1) isn't this you being arrogant.
2) some of these visionaries would disagree with you.
The beautiful attractive idea you have is not grounded in reality.
Your ideas about God may be just peachy, but your ideas about other people's ideas are distorted by this beautiful idea you have. This need for these religions to be one because, I can conclude, you see division and against God.