Why did the Son become incarnate? Because he submitted?

The following article is from Dr. Mark Jones. I am grateful for his labor and sobriety over this matter.
Most debates I read of today have a parallel with another debate that has taken place over the course of church history. For example, the seventeenth-century Arminian theologian, Simon Episcopius, located the Son’s submission in an inherent subordination in the deity of the Son to the Father. He was not just claiming a certain order of subsistence or even speaking of an ontological dependence of the Son on the Father in terms of persons-appropriate language. That would not be controversial. 
Rather, Episcopius argued that the subordination of the incarnate Son, which was traditionally ascribed to his voluntarily (i.e., freely) undertaken redemptive work, is in fact properly characteristic of the Son’s intrinsic relation to the Father. Even apart from the consideration of God’s ad extra (outward) works, there is, for Episcopius, an eternal (necessary) submission. This view of Episcopius may be the most obvious and similar precursor to present-day views that speak to “eternal submission.”
Using phrases such as “eternal submission” suggests there is an ontological submission of the Son to the Father in the ad intra relations between the divine persons. But how, given there is one essence (and thus one will), there can be submission is utterly beyond me.
There are a number of perspectives we could approach this debate from. Here’s one that many haven’t given much attention to as of late, which is why I raise it:
Why did the Son become Mediator? 
Was it because he is eternally submissive to the Father? Does the Son have a relationship of submission to the Father in eternity? 
Remember, Denny Burk, defending Ware and Grudem, speaks of “eternal submission”:
“Trueman acts as if the eternal submission of the Son to the Father view is some new teaching that has been sneaked into backdoor of the church while no one was looking. This too is absurd.”
First, I don’t think Trueman made that point; but, second, note the precedent above with Episcopius – the Arminian. It is a well-known fact that Arminian Trinitarian theology had certain flirtations with Socinianism. Ideas have consequences, whether we like to admit that or not.
Bruce Ware has made the point: “Therefore, as we consider the incarnational mission of Christ, with the Son expressing his own submission to the Father with words such as, ‘I do nothing on my own authority, but speak just as the Father taught me’ (John 8:28), we see that this same relationship of submission to the Father was true in eternity past, even before the creation of the world. The submission of the Son in the incarnation is but a reflection of the eternal relationship that has always been true with his Father. The Son always seeks to do the will of the Father, and this is true eternally.” Bruce A. Ware, Father, Son, and Holy Spirit: Relationships, Roles, and Relevance (Wheaton, IL: Crossway, 2005), 79. 
This seems to me to be very dangerous language when speaking of eternal relations. There are all sorts of theological issues that arise out of this, especially in relation to Christology. (I plan to address this in the future, as well).
For my own part, I do not think that Bruce Ware or Wayne Grudem are using phrases and language that is helpful. The language of subordination, submission, etc. needs to be removed from our discussion of ad intra eternal relations between the three persons. 
Matters are different in regards to Christ and God the Father because Christ has two wills. I worry that Ware may be forced to affirm monothelitism or a version thereof because of his position. 
So why did the Son become Mediator?
Because the Mediator must be God, redemption requires that one of the three persons becomes the Mediator (and thus the God-man, with two wills). 
1) The most basic reason has reference to the doctrine of the Trinity.  
The idiōmata (proper qualities) and titles by which the Persons of the Trinity are distinguished should be kept and preserved distinct.  
The Son of God is, by virtue of his title, more appropriately the Son of Man and the Son of a woman.  In other words, it was not “fit” that in the Trinity there should be two persons who both bear the title of “Son,” which would have been the case had the Father become incarnate.   
Turretin argued that the Holy Spirit, for example, could not be sent to be Mediator because “there would have been two sons, the second person by eternal generation and the third by an incarnation in time.”  
Therefore, the order of subsistence among the persons of the Trinity is decisive for resolving this question. The order between the three persons is maintained in the Son becoming the Mediator, since both the Son and the Holy Spirit being from the Father in subsisting, are not to send the Father, who is the first person. 
Thus, for the Reformed orthodox, the order of subsistence among the persons of the Trinity reflects the order of their work.  
2) Again, grounding our argument in the order of subsistence between the three persons, the Son, as the “middle person” bears the best resemblance of the work as Mediator. He comes between us and God. 
Turretin argues that “he who is between the Father and the Holy Spirit should be Mediator between God and men.”         
Consequently, the Reformed orthodox maintained that the Son should be Mediator based on the order of subsistence. 
3) The Son is peculiarly fitted to be Mediator since, according to Thomas Goodwin, “the main end of his being Mediator,” that is, the adoption of his people into the family of God, is “made one of the greatest benefits of all others” (Eph. 1:5).   
The Son is the most suitable person to convey this soteric blessing insofar that as a Son Christ conveys sonship upon his people by virtue of his union with them (Gal. 4:4-5).  
Again, in similar fashion, Turretin argues that it was fitting that “he who was a Son by nature should make us adoptive sons by grace.”  Besides Trinitarian reasons, soteric factors – i.e. the doctrine of adoption – explain why the Son should be Mediator. 
4) The offices of the Mediator, namely, priest, prophet, and king, necessitated that the Son of God take on the work of mediation.  Regarding the office of priest, it is the birth-right of the eldest Son in the family to be the priest. Therefore, to prove he was a Priest (Heb. 5), the author cites Psalm 2: “You are my Son, today I have begotten you.” As an intercessory priest the Son is uniquely able to approach the Father, which is a function grounded both in ontology (i.e. their natural subsistence) and economy (Christ’s work of mediation).  
As a prophet, the Son is especially fit to be Mediator because he is the Word and Wisdom of the Father (Heb. 1:1; Jn. 1:18). 
5) As a King, there is none so fit as the heir, “none so fit to have all Judgment and the Kingdom committed to him as God’s Son” (Goodwin). 
In the future, I want to take up the issue of using the language of “authority” and “submission” to describe ad intra Trinitarian relations. It seems to me to be highly problematic, as many have pointed out, to make “submission” the constitutive personal property in God. (I also want to challenge Bruce Ware’s use of the word “eternal” in his Reformation21 piece, which to me is an example of failing to understand how the term has been used historically. And, as I noted above, his Christology seems to have suffered as a result of his Trinitarian views).
There are better ways of understanding why, for example, the Son became Mediator. Those ways do not require us to use the language of submission when it comes to the eternal relations between the Father and the Son. 
For my own part, I am not suggesting that these men are going to hell because of these errors, as if they were rank heretics. But I do think we need to be prepared to challenge each other, sometimes strongly, when such important truths are at stake.