Could you please show me in scripture where another "man" has the right to determine the legitimacy of a divorce if it was enacted by the husband and meets scriptural standards? If it doesn't meet scriptural standards then its not a scriptural divorce regardless of what any man say's.
Certainly the question is whether a divorce meets scriptural standards. However, life is messy, and it can be difficult to determine whether real-world situations actually meet those standards or not. A woman for instance may have had a past relationship that was terminated by her drunken partner shouting "get out of the house b*tch" and throwing her out the door. She doesn't return, and a few years later wants to remarry. Does an angry expletive-ridden statement issued under the influence of alcohol (so possibly not carefully considered) constitute a legitimate divorce initiated by the husband, or does it not? Don't try to answer the question, that's not the point - I'm just giving an example of a realistic situation that is not clear-cut.
Proverbs 11:14 "Where no counsel is, the people fall: but in the multitude of counsellers there is safety."
In this case, a wise course of action could be to take this matter to the elders for an answer. The elders are not being asked to make the divorce legitimate or illegitimate - no man has that authority. They are being asked to figure out whether it meets scriptural standards or not. The man could say to the elders "I don't know the answer, and I am emotionally involved so could make the wrong judgement, I will trust you to give an impartial and considered analysis of the situation and marry or refrain as you advise". This would be a wise and humble approach to the situation.
The marital union is between, A man and A woman and God.
Not to go down too much of a tangent, but that isn't scriptural (find one verse that says it). The marital union is between a man and a woman. The two are put together by God, but he is not a party to the union, just the matchmaker. This teaching is a very common statement by monogamist preachers, and is a misinterpretation of "a three-fold cord is not easily broken", with the three-fold cord being called the man, woman, and God. In context, that statement is simply saying that in all areas of life, a team of two is better than an individual (because it can achieve more), and a team of three is more resilient because it is "not easily broken", ie even if one fails you're still left with a team of two. This is not about marriage specifically, but about all teams, whether in the context of business, military, marriage, or any other situation. Can elaborate more if you like, but we should probably go to a different thread for that.
<regarding "A" wife> This possibility cannot be correct as 1 Cor 7:8 shows Paul to be single and thus he would be stating that he himself did not meet his own requirement.
By that logic, "one" wife is also an incorrect translation, as Paul was single and thus did not meet the requirement to have "one" wife.
Another point to ponder: was Paul an elder? Or was he a travelling missionary, who appointed local church elders but did not himself have to conform to the standards expected, as his job was quite different, and being single was actually beneficial in his case?
That would however mean one standard for those in oversight and another for the individual christian man that was not in oversight. This however was the case for those in leadership under the law of Moses as a priest was restricted in who he could marry but the average man could marry the women that a priest was forbidden to marry, thus two standards for the same people dependent on the responsibility's held. Thus it would not be a change or even be speaking against the law, just an organizational arrangement to protect the Church from opposers.
It would be a change in the law, as it would be completely changing the standards. In the Mosaic law a priest could be polygamous, but could not marry a divorced woman or prostitute. In Paul's writings he never discourages church leaders from marrying such women, on the contrary the whole general thrust is that the old has passed away and has been forgiven, so a prostitute is completely free to marry with no restrictions on whom - but then it is suggested that he is requiring them not to be polygamous. This would arguably be a complete reversal of the law - if the interpretation is correct.
I do see your point about protecting the church from criticism. And I actually agree, in many situations being monogamous would be advantageous for cultural reasons. We are to do whatever we can to meet people where they are at in order to preach the Gospel to them without turning them away, and therefore I can certainly see many situations where being polygamous could be a problem for a particular individual. Each of us must certainly follow God's direction in our own lives. However it is a large jump from that to an outright ban on polygamy for all church leaders for all time and in all cultures.
The fact is if the law of the land was to be enforced to its maximum degree in this matter who would lead the flock (even today)?
Polygamy is not illegal, in most countries. A very small number of US states, and Canada, have laws against polygamy. For the rest of the Western world and much of Asia, you can live with as many women as you like. While in Africa and the Middle East polygamy is generally legal in one form or another. Western countries do have laws against bigamy (registering two simultaneous marriages with the State), but that's a very narrow situation that doesn't apply to many people. You can have as many simultaneous relationships as you want, completely legally, and many secular people already do. Most of these laws are already enforced strictly, yet don't affect us at all. So this is not a valid concern today.
Even in Roman law, although a man was only allowed one "official wife", he was allowed as many concubines as he liked. So polygamy was not illegal even then. And the Roman empire did not enforce such laws in occupied territories during the time the New Testament was written, I understand laws mandating monogamy were not enforced through the empire until after 300AD, after the adoption of the Catholic church as the state religion. The culture of the people Paul was writing to was one where prostitution was extremely common, the general public had no issue with men sleeping with multiple women so this would have been unlikely to cause outsiders to judge the church negatively. This does not seem a likely reason for such a restriction.
Back to church elders specifically - this is not usually interpreted to mean "precisely one wife", but rather "no more than one wife". An elder whose wife dies will not lose their job, as nobody is so strict as to interpret this to mean exactly "one". The standard church teaching is "no more than one wife". And this is an addition to scripture, because that is not what the verse says - it just says "mia", "one". Is it not equally valid to interpret it as meaning "at least one wife"? Andrew is an elder of this ministry, and he has one wife. He also has another two wives - but does that change anything? How is it any different to a widower being an elder? Either way you can get tied in knots about it.
I personally feel that the interpretation of "first" (or "number one" to put it a different way) is by far the most likely, as it is consistent with the general encouragement of men to be faithful to their wives. It means in effect, that we are to be faithful to our wives and not unjustly divorce them, and elders are to be men who model this faithfulness. If these passages introduce a requirement to be monogamous, this is a sudden imposition that is not even hinted at elsewhere in scripture and suddenly appears in the writings of only a single person (Paul) with no explanation - this is not established by at least two witnesses. However if they are about faithfulness, they are completely consistent with the remainder of scripture and give a practical application of the principles already outlined in many places throughout all of the Bible.