What is the ruling on a man marrying his daughter to another man’s son in exchange for the other man marrying his daughter to the first man’s son, provided that a mahr (bridal gift) is paid in both cases?

Eid Abbasi : The questions received from our brothers, first: What is the ruling of the Shari'ah regarding al-badilah? This is when a man marries his daughter to the son of another man, and the other man marries his daughter to the son of the first man, with each having a mahr (bridal gift). Even if one of the sons leaves his wife, and the other has no connection to her and is not harmed by it; knowing that the two wives have already borne several children, and after twenty-five years have passed, one of the scholars issues a fatwa that it is obligatory to separate each husband from his wife; is this correct or incorrect? And so on.

The Shaykh : If it is as the scholars say, "A fatwa is based on the extent of the text," meaning that the questioner has accurately described the reality, then the answer is that this marriage is valid. This is because some of the Shaykhs who ruled on the necessity of annulling this marriage assumed that this marriage was shighar. The Messenger of Allah (peace and blessings be upon him) prohibited shighar in more than one hadith, and he said: .
However, the scholars differed regarding the essence of shighar: what is it? In its original form, it is when a man who has a daughter and another man who has a daughter exchange them, so each one takes the other’s daughter. This is the origin of shighar. Then it comes... and it is not limited to a specific case involving a daughter; if one has a sister and the other has a sister, and each takes the other’s sister, this is also shighar. But the complete form of shighar is when each one makes his mahr, which is his obligation, his sister or daughter whom he presents to the other, as if it were an exchange of goods for barter. Naturally, this is not permissible in Islam, because in this, the right of the daughter, which is the mahr, is negated. From here, the disagreement begins. So, part of the complete shighar is that one of the husbands gets angry for some reason with his wife and divorces her, so she goes to her brother or her father, and the other one, in turn, divorces the sister or daughter he has, and thus shighar becomes a cause for increasing separation and the occurrence of divorce between the married couples. This is shighar, which was known in the pre-Islamic age of ignorance (jahiliyyah), and which the Messenger of Allah (peace and blessings be upon him) prohibited.
As for if it is not of this shighar except a mere exchange while fulfilling all the conditions of marriage; I have my sister and I gave this sister to a person named Zayd, and in return he gave me his sister, but each of us gave what is obligatory of mahr, this is on one hand, and on the other hand, we do not link the fate of the wife we have with the other; and if one of them is angry, she manages her affairs with her husband, and the other remains with her husband. So, if it is a mere exchange without what? Considering the complete pre-Islamic shighar; meaning like a man who took a relative’s female relative, and gave his daughter or sister to a relative of his; then there is no harm in it at all, as long as the mahr is present, and as long as the condition of divorce in exchange is also not present. So, if the incident is as the man mentioned, according to what I understood, then this marriage is not shighar; as long as each one paid the mahr, and each one adheres to the Shari'ah etiquettes between him and his wife.
But what we fear is that there may be some details in the incident that the questioner did not cover, or perhaps the questioner covered them but the Shaykh who issued the fatwa did not cover them, so he issued a fatwa on the invalidity and nullity of this marriage.
Other than that?