One of the anachronisms of the "Presbyterian" church is that the modern understanding of elder, whether one office, or two, is not consistent with the tradition of the church. I don't have a lot of scriptural opinions on church polity, other than to complain that youth and seminary training seem to do more harm than good.
The traditional view is rooted in the synagogue. The synagogue would be led by the priests and Levites who were God-ordained to prophesy and work among the people; however, there were also lay leaders, called elders, who governed the synagogue. Whether the practice of the synagogue is normative for us today is a good question, and perhaps the interpretation of e.g. the Westminster Assembly is not a correct understanding, but it was the view of the Reformed church at that time.
According to Peter Colin Campbell, in his book The Theory of the Ruling Eldership, Westminster specifically, and unanimously, denied that "ruling elder" was synonymous with the elder of the New Testament (p.33-34)
From the record of that Assembly left us by Lightfoot and Gillespie, we learn that the discussion on the point of lay elders in the Grand Committee, commenced on the 12th of November 1643, and lasted with some interruption till the 11th of December, a period sufficient to show how carefully and anxiously it must have been conducted. The subject was introduced for consideration by a proposition so framed as distinctly to bring under discussion, not merely the lawfulness and expediency of the institution but the special theory of Calvin: "That besides those presbyters that rule well and labour in the word and doctrine, there be other presbyters who especially apply themselves to ruling though they labour not in the word and doctrine." The discussion which follows is instructive, and the result remarkable. While the Grand Committee declare unanimously in favour of the institution of lay rulers in the Church, they carefully exclude from their conclusion not merely the term presbyter, in reference to lay rulers but even that of elder, as liable to be confounded with "presbyter," and refuse to quote 1 Tim. v. 17, in regard to the office. The conclusions of the Committee are recorded thus by Gillespie and Lightfoot:-
"1. That Christ hath instituted a government and governors ecclesiastical in the Church.
"2. That Christ hath furnished some in His Church with gifts for government, and with commission to execute the same when called thereunto.
"3. That it is agreeable to and warranted by the Word of God that some others besides the ministers of the word be church governors, to join with the ministers in the government of the Church Rom. xii. 7, 8; 1 Cor. xii. 28."
... "there fell a debate about naming church governors, whether to call them 'ruling elders' or no; which held a very sad and long discussion: at last it was determined by vote thus, - such as in the Reformed Churches are commonly called 'elders.'" Gillespie made a last attempt to obtain the recognition of the theory, and, with obvious purpose moved that the Assembly itself should call them "ruling elders;" "but this," Lightfoot tells us, "prevailed not." The battle of the presbyter theory had been fought and lost
Campbell explains that Scotland (whether ignorantly or purposefully) did not remove the "ruling elder" language from their own ecclesiastical documents, which led to a resurgence of the idea of 'elder' as 'presbyter'.
The effect [of the lack of removal] was that which in all probability the Westminster Assembly had desired to prevent. The use of the designation "ruling elder" kept the popular mind unavoidably directed to "the elders that rule well" of 1 Tim. v. 17, and maintained a measure of life in the theory, quietly buried at Westminster with the formal assent of the Scottish Church, which regards the lay rulers as a portion of the presbyterate.
In the "Presbyterian" church (which is synonymous with those churches descended from the Scottish churches), this misunderstanding is perpetuated, and anachronistically considered the historical position of the 1st century church.
As I said, I (now) don't have a really strong opinion on who gets to be ordained and who gets to participate in various aspects of the life of the church, but I do think this warrants the following discussions:
Minimum pastoral age
Considering that "presbyter" literally means "old guy", like "presbyopia" is the inability of older people to focus on close objects, the status quo of seminary-trained 20-something pastors is likely a really bad idea. Proponents of "classical presbyterianism" will argue that it's okay for the ministers to be young because "the ruling elders are the old guys", but this is clearly not what Westminster unanimously decided. They stated that presbyter, overseer, minister and elder were all aspects of the same office. The Bible seems to distinguish knowledge from wisdom, with wisdom being closely coupled with life experience. A 26-year-old RPTS graduate likely has zero, or nearly zero, life experience, but lots of Seminary-derived knowledge and youthful vigor. This has become the culture of many churches, where knowledge and vigor have become proxies for Spiritual giftedness. Does a presbytery exam really determine wisdom, or can RPTS "teach to the test" to give their students what they need to appear wise? How can we determine if, for example, a candidate is a good father, if his children are still toddlers?
Plurality and geography
Part of the Presbyterian system is a plurality of elders. If there is only one "elder" in a church, there is hardly any accountability. The RPCNA tries to create that accountability by elevating the lay leaders to equal in rule and judgment, and making the pastor a member of the congregation, subject to the Session, but if "lay leaders" do not rule in that sense, there is a vacuum of leadership and accountability. I think this is evident in the RPCNA because the pastors in the Presbyteries are not holding each other accountable, unless there is clear heresy rising to that level. When we picture a "church at Ephesus", Timothy might be a senior pastor, but there would be a plurality of pastors within the city who would have much closer oversight, not just a quarterly get-together of forty guys serving a geography of maybe 1/3rd the United States.
Seminary
Maybe this follows from the other two, but if you have a plurality of pastors in a geographical area and there are people in the congregations who have demonstrated a lifetime of wisdom, they have also gained a lifetime of knowledge. So, perhaps the knowledge gap of a 40-50 year old who feels called to minister is much less dramatic than someone whose brain still hasn't completely formed. Even then, seminaries cannot fix the problem of 18-year-old know-it-alls who have been fawned over by their congregations and presbyteries. Their hubris just becomes calcified and now they are an ordained know-it-all minister with zero life experience, but an M.Div and an ordination who holds all the authority in the congregation.
Also consider that someone who has been pastored, discipled and mentored for decades has much more of a base to draw on than someone who has a high school diploma and three years of seminary. So, seminary could bring much more depth.
I also have very little interest in the argument about understanding original languages. I'm sure it's helpful, but is it a necessity? Maybe a pastor who knows Greek understands more than that same pastor not knowing Greek, but does a pastor know more than a Greek scholar after two or three semesters of Greek? Doubtful. Does a generic Greek scholar know more about a passage than someone who has spent decades studying the context of a passage? Doubtful. So, I can, most likely, know more about a passage by reading commentaries and books by Greek scholars than I can by knowing enough Greek to be dangerous and cowboying it. This also feeds into pastoral hubris.
Ordination and office
The RPCNA struggles with this. Pastors are ordained by the Presbytery, while ruling elders are ordained by the local Session. The inherent unfairness of considering Ruling Elders "equal" to Teaching Elders is obvious here, and highlighted by, e.g. the "ordination" of Kent Butterfield. Kent was already an RE when he decided to become a pastor. The GLG Presbytery could not re-ordain Kent when he was called to a church, but it was (apparently) insufficient given the gravity of the situation to do nothing, so they fake-ordained him. In other words, they had him kneel, they laid hands on him, but they did not pray the prayer of ordination.
In the same way, the RPCNA calls the ministry of the word a "distinction":
The responsibility of the elders is in teaching and ruling. Although all elders are to be able to teach, the Scripture recognizes a distinction in these functions. (RPT 25:9)
yet prohibits or restricts ruling elders from many ministerial functions, except in "special circumstances"
The Sacraments of Baptism and the Lord’s Supper agree, in that the author of both is God; the spiritual part of both is Christ and his benefits; both are seals of the same covenant, are to be dispensed by ministers of the gospel and by none other; and to be continued in the Church of Christ until his second coming. (WLC A176)
The sacraments of the New Covenant ordained by Christ are two: Baptism and the Lord’s Supper. They are to be administered according to Christ’s appointment, by pastors or by ruling elders authorized by the presbytery to meet special circumstances. (DFW 3:2)
Ordinarily, a teaching elder is the moderator of the session. Extraordinary circumstances may arise where it is advisable for the session to elect as moderator an elder other than the teaching elder, or for the moderator to be appointed by presbytery. (DCG 4:2)
Even in discipline, they are considered different. Ruling Elders can be deposed by their Session, but not Teaching Elders.
I'm curious what others' thoughts are. My current feeling is more of a one-office view where the leaders of a local church are all ministers of the word in some sense with equal authority. There may be a hierarchy in the sense of having a senior pastor who is more respected and trained, but many of the issues go away when the ministerial staff isn't one more seasoned pastor surrounded by puffed-up knowledgeable bundles of vigor driving the sheep. I also think that much of the ministry of the church can be done by all members, or even non-ordained members in lay office, like a treasurer, or, dare I say, deacon.