Angels are important in faiths like Judaism, Christianity, Islam, and also in others. Therefore I propose you to take account of this state of affairs in your picture.
First of all let me say that my understanding of both God and humanity is based on the fact that God created humans (male and female) in God’s own Image, and also that Jesus Christ is Very Human of Very Human and Very God of Very God.
This means to me that God is Personal. in that humans are personal being, and God as YHWH in the OT, God the Father in the NT, and Jesus Christ are all Persons in the current meani8ng of that term. Also that humans have the ability to create through their bodies, to think through their minds, and love through their spirits, while God the Father has the power to create as the Creator, God the Son has the power to think as the Logos, and God the Spirit has the power to love as the character of God.
You say that God created angels as purely spiritual beings, who have free will. I question the re3ality of angels and say that they do not have free will as portrayed in the Bible. The Bible indicates that some angels rebelled against God, so this would seem to indicate that they have free will, but it also says that these fallen angels cannot repent and be saved by Jesus so how can we say that they have free will.
If angels are purely spiritual beings as you say, how can they think and how can they act? If angels are created beings, then why do they not die? If God created beings who had free will, then why did God create human beings who also had free will, but were mortal?
Angels are not essential to God. It appears to me that they evolved from the sons of God (Elohim) to agents of YHWH. As I said they are needed in Judaism and Islam where God is One and angels serve as a buffer between Elohim and Allah.
In other words in a complex world angels serve as mediators between the One and the many. For Christians Jesus and the Spirit serve as mediator and conduit between the Father and humans. There is no theological need for angels, because Jesus Christ is God with us and God for us.
In particular, regarding the Christian teaching about Trinity, it is important to distinguish between the “Many” as referring to the three divine Persons (Father, Son and the Holy Spirit), and the “Many” as referring to the multiplicity of beings outside God, in particular angels.
Humans are complex/one beings, who live in a complex/one world, and need a Complex/One God. Angels began as false gods, but became agents of God. They can be seen as the complex aspect of YHWH and Allah.
I recently read that theologians insist that the Christian Trinitarian God is Simple and not Complex. This has to be the result of the influence of Greek philosophy that insists that Being is Simple and not NT theology. Again YHWH, the Father, and Jesus Christ are not simple Beings.
God is One, but God is not Simple. God cannot be less than humans. God cannot be less than angels.