We use 'one' to talk about a generalised concept of people in general. It is an indefinite personal pronoun, and cannot be used as a gender-neutral substitute for 'he' or 'she' when talking about the Christian God. There is little agreement among Christians about how to do this, or whether it is necessary. The Church of Sweden made the decision in 2017 to simply use 'God' instead of either human-gender personal pronoun. The head of that church said, illustrating the usage: ""theologically we know that God is beyond our gender determinations, God is not human". Some Christians, however, feel that such usage undermines the doctrine of the Trinity (Father, Son and Holy Ghost) because it de-masculinises the "Father". Some churches try to give both sexes equal time by alternately using 'he' or 'she'. The Church of England Bishop of Gloucester, Rachel Treweek, adopts the Swedish practice, and has said that God should not be referred to as “he”. She says, “We’re told that God created human beings in God’s likeness… If I am made in the image of God, then God is not to be seen as male. God is God.”

[Gender neutral pronouns for God][1]

  [1]: https://www.refinery29.com/en-gb/2017/11/182953/church-gender-neutral-pronouns-god