Married For Real Or For Fake

I recently saw an interesting question in a contemporary sefer. There is a Rav whose job is to marry off couples who are not religious. The problem is that many of these couples will end up not being faithful to each other and/or get divorced without a proper get. This will mean that they will commit very serious aveiros and bring mamzerim into the world [as a woman who doesn't receive a get causes her future children to be halachically illegitimate]. He wanted to know if he should fake it and make sure they are not halachically married. He will set aside invalid witnesses ["We'd like to call up the brother and sister of the Kallah as witnesses"]. Then he would tell the choson to say הרי את מקודשת without the word לי which also invalidates the marriage. This way he would save them from sinning in the future. If and when she has an affair it won't be halachically considered cheating on her husband because they are not married.

The problems are that to live together as non-marrieds is also forbidden according to the Torah [albeit a lesser sin that adultery]. Another problem is גניבת דעת - misleading another person. An additional problem is that if they find out that they were fooled it will be a chilul Hashem. Also, if the Rav is being paid for this he will be receiving money for services not rendered. Also, the eventuality of infidelity is not 100 percent whereas the sin of living together without being married that he wants to cause them to commit [to save them from a greater sin] IS 100 percent so maybe it's better to hope they don't sin later and to conduct a proper marriage now.

Also - I don't like shtick.... [but then again I wasn't asked and maybe he is saving the woman from a חיוב מיתה].

See the surprising conclusion in the שו"ת תשובות והנהגות ח"ד סי' רפט [the only teshuva I ever recall seeing of Rav Shternbuch where he quotes a Rebbe from YU].