I beg to disagree. I recommended my relative who does not pray to marry a loving kafir simply because in my humble opinion he would do her good. Alhamduillah, they married and of course he converted, now he is an imam and she has become a devout Muslim praying 5 times daily. I knew getting her married would be a wise decision because Rasul said one who marries already covers 50% requirement of being a Muslim and I knew Allah in His wisdom would guide the way.
You are giving an isolated example. I'm sure that has happened in a few cases by the will of Allah. But what about the many cases where that has not happened and consequently has led to marriages being destroyed or even invalid because the person didn't change/revert or they reverted only to marry the person but did not become practicing?
Guidance is not in our hands, so even if the entire world were to get together to try and guide somebody on the right path, then if Allah does not will for them to change then they will not. This is due to some fault and discrepancy of their own that is preventing them from changing. I know personally of many examples of both men and women who married people hoping they would change after marriage but they didn't and in fact many became even worse. This is also one of the reasons why pre marital relationships are condemned in Islam because once a person falls for the person then they can become blind to the fact of whether or not the person is good for them as a spouse.
So we should never advise anyone to marry someone who is not practicing in the hope they will become practicing at some point after marriage as it may or may not happen which can result in dire consequences for the couple and children involved.
Islam already gives us the criteria of what to look for in a potential spouse:
The Prophet (Sallallahu Alaihi Wasallam) said: “A woman is married for four things, i.e., her wealth, her family status, her beauty, and her religion. So you should marry the religious woman; (otherwise) you will be a loser.” (Al-Bukhari)
The Prophet (Sallallahu Alaihi Wasallam) said, “If someone with whose piety and character you are satisfied comes to you, then marry him. If you do not do so, there will be disorder in the earth and a great deal of evil.” (At-Tirmidhi and others and classed as Hasan)
The Prophet (Sallallahu Alaihi Wasallam) praised a woman with good religious qualities, saying: “shall I not inform you of the best treasure that a man gathers-A righteous wife.” [Reported by Al-Hakeem].
Allah says: “Bad women are for bad men and bad men are for bad women. And good women are for good men and good men are for good women.” (An-Nur 24:26)
“and verily, a believing slave is better than a (free) Mushrik (idolater), even though he pleases you” [al-Baqarah 2:221]
Ibn `Abidin, a famous Muslim jurist, said: “The woman should choose a man who is religious, of good character, generous and of ample wealth. She should not marry an evildoer.
A man said to Al-Hassan Al-Basri (Ra): “To whom should I marry my daughter?” Al-Hassan said, “To one who fears Allah or if he comes to love her, he will honour her and if he dislikes her, he will not oppress her when he is angry with her.