Hi Nick,
I agree that the Father and Son are of the same nature, however, I don't believe they are equal regarding order. I also don't believe that the Son, existed as a separate entity from eternity past. I believe He came forth from the Father and was eternal in the sense that whatever the Father is (substance) the Son is. I like to use the EFC example of fire. If you place a stick into a fire it ignites and becomes a separate fire, however, the first fire is in no way diminished. The second fire came into existence as a separated fire at a point in time after the original fire and yet the second fire existed in the original fire from the beginning and as such existed as long as the original fire even though not as a separate fire. I believe that the Son, now is in the flesh and thus doesn't have all of the qualities that the Father has. Paul said that the Father alone has immortality, so I believe the Son receives life from the Father.
We're close to agreeing, but I have a few caveats.
I don't believe Paul ever says only the Father has immortality. You'll have to cite that.
I don't believe Christ came into existence at a particular time, because he was with God and was God in the beginning. I believe the Son came forth from the Father, but I believe he has existed eternally. I think it's a mistake to push the language too far, because Scripture upholds both these things as true. It becomes meaningless to try to pin down a time where the Son came into existence, because existence/non existence has no meaning if there is no time. No time, no true causality. Instead, the language is meant to teach us something of the relationship of the Father to the Son (the Son proceeds from the Father) while maintaining the basic ontological reality (the Father and Son are of one substance - that is, the eternal substance).
I also think it's a mistake to talk of God as consisting of separate entities. They are not separate, but they are distinguishable. If Christ is of the same substance as of the Father, he is eternal, because that's the essence of God.
The Son in the flesh doesn't diminish his qualities, although he put off (the language of Phillipians 2) some of the aspects of his divine nature in humility in the incarnation. That, of course, doesn't speak at all to his qualities after resurrection and ascension, where he is exalted to the right hand of the Father, has the name above every name, to whom all will bow, and by whom all will be judged.
There is a difference in order, I feel, but we can overemphasise the order, and make it a question of raw ontology, where I think Scripture's account is quite a bit more nuanced than that. Does the Son submit to the Father because he is the Son? Yes. But the reality is still that the Son has life in himself, and is ascribed the role of creator -which historically, much more so than today, has immense connotations in terms of authority, status, and divinity.