I think it is necessary to assume that God had at least two goals in creation.
The first was to create Heaven - which means to create a world ruled by love. I tend to think of Heaven as a place where all relations between beings are loving - love, not coercion, is what gives cohesion to Heaven.
And I assume that any being can enter Heaven who is prepared to discard everything of himself which contradicts the primacy of love.
But God wanted more than this.
As William Arkle describes it - God did not want to remain 'alone, but God wanted divine friends.
God wants not just 'children' (immature, undeveloped sons and daughters of God, like most mortal Men) - but God wants some of these children to grow-up to become like himself: that is a fully creative being - a being able to continue and enhance ongoing divine creation.
So divine creation makes this growing-up of men to gods a possibility. Everything is provided to enable this to happen for a Man - except the vital ingredient that a Man must want it.
Overall, God wanted a Heaven in which dwelt other gods. (...As many as possible, each unique.)
That is what God is working-towards, by means of creation.
In other words, to summarize the argument; behind divine creation is God's desire for a loving Heaven that includes (but does not consist entirely of) many other gods, of the same nature and type as God-the-creator.
To become a god, a Man must want to become a god - that is, a creator on a level with the prime creator, albeit working within God's prime creation...
(Why must he want it? Because a god must be conscious to be free; God must be conscious to be an autonomous agent of creation. An un-conscious 'god' would simply operate as a tool for creation - he would not be a god.)
But that is not enough. As well as desiring full divinity; a Man who wants to become a god must also want to enter Heaven.
That is how God set-up reality.
One can have Heaven without wanting to be a god - e.g. wanting to remain a child; but one cannot become a god without also wanting Heaven.
To be a god outside of Heaven is forbidden, it was made impossible.
Theosis is only made possible to those who want to become a god - i.e. by those who will enter Heaven.
Salvation to escape sin and dwell forever in Heaven is available only to those who will make an eternal commitment to live by love.
Theosis and salvation are thus bound-together and made one by resurrection.
It is only by resurrection that a Man is made both eligible to enter Heaven and takes a decisive step towards the eventual goal of becoming A-god, like-unto The-God.
Therefore, salvation is primary and must come first, before full and permanent theosis is possible. But theosis is the reason for creation, the reason for Jesus Christ, and the highest desire of God.
Notes: When I write 'God' in the above post, I mean the Christian concept of God.
The God/s of other religions are differently motivated - and non-Christians do not intend that Man should be raised to the level of full-creator God: i.e. to that level of divinity which Christians believe was seen in Jesus Christ. This elevation of Man to god is the possibility of which Jesus offered to those who believed-on and followed him - an equivalence of status whereby Men are regarded as 'friends' of God, not as 'servants'.
I have also deliberately left open the structural aspects of the Christian God: I personally believe (with the Mormons) that God is our Heavenly Parents - that God is a dyad of Father and Mother; but the above argument works also for the more common and 'traditional' Christian trinitarian monotheism - where the love of God originates from the triadic love of Father, Son and Holy Ghost.
Also, I believe that the above scheme can be discovered from reading the Fourth Gospel ('John'); when that Gospel is assumed to be the primary and qualitatively most authoritative account of Jesus's life and teachings.