Building on my previous enquiry into the Divine references in this chapter I am interested to know why Paul would state 'God Father' in verse 1.
With the coming of Christ, the promised Messiah, the Son of God revealed that 'God' is his 'Father' and that 'God' is also 'Father' to the redeemed. His purpose is to bring many sons to glory, Hebrews 2:10, and Jesus calls him 'Father': on one notable occasion addressing a whole chapter of prayer to him, John 17.
Then if it be firmly established that 'God' is 'Father' why use both words in this verse, not once but twice ?
If this be regarded as two nouns in apposition (the construction in which, it is said, two elements identify one concept in two different ways) then why does Paul need to identify one Person by two different means ? If God always equals Father and Father always equals God - why say it twice ?
To say 'Father' is to both convey his deity and to convey his fatherliness. Both have been adequately established.
To say just 'Lord' could be ambiguous. There is 'Lord God' and there is 'Lord Jesus Christ'. So just to say 'Lord' requires more to be stated. There is dominion within the Body of Christ and there is dominion over all - Lord God Almighty. (All things shall be subdued under Christ, but not yet, I Cor 15:28.)
But if 'God' be only 'Father' and none other, why say 'God Father' ?
To say 'Father' is to assert all the deity that exists, in that one person - if only one person is Divine.
And as with the word 'Lord' there is never any need to distinguish between earthly lords and heavenly Lord for context is always sufficient to do so. Thence, also, context will always distinguish all earthly fathers and the only heavenly Father. There is no need to say 'God Father' to distinguish from earthly fathers.
Is it not the case that Paul says 'God Father' because he wishes to convey both deity and person. And in order to distinguish person (within deity) he says 'God Father' : thus demonstrating that more than one Person possesses Divine Being.
What other explanation could there be ?