If he doesn't like that promise, then he doesn't make it. Perhaps he tries out "love, honor, and cherish til he decides to change his mind." And if his fiancee walks out of the marriage ceremony because of it, that's her choice too. If she accepts it, and he does change his mind later, then she must accept the consequences as well.
If you make a promise, then keep it! If you can't keep it, then don't make it. The problem with most marriages today is that the couples simply do not understand their vows; or they believe that any interpretation of them is relative and acceptable.
Here's what my wife asked me before we got married. She said to me, "will you promise to love, honor, and cherish me so long as we both shall live?" And I said yes. And she said, "that promise is still in effect even if I go out and cheat on you and have babies with other men and leave you." And I said, "I know. That's what a covenent is, unlike a contract. If you cheat on me, that doesn't give me right to cheat on you. And of course the same goes for you too. And if you do, it doesn't mean that I'm going stay with you and pretend like nothing happened. It just means that I will never cheat on you in spite of your actions."
So we made our vows--covenently, not contractually. And because of that, if one of us does cheat on our vows, that person should get no special attention in the eyes of the law, and all benefits should remain with the one that kept his or her vows.