I think that Czy wyjdziesz za mnie? is just a point of departure. To my way of thinking, this question - undoubtedly one of the most important ones in your life - is quite personal, and thus you can personalize it in any way you like. I, for instance, would prefer something like Imię (ewentualnie "Moja droga" czy coś w tym stylu), czy uczynisz mi ten honor i wyjdziesz za mnie, which means Name (optionally "My dear" or soemthing like that), would you do me the honor and marry me?.
A Middle-Age Knight is much better than a mucho: hajtniesz sie ze mną?
I agree whith Majlo. There are so many situations and people, there to find suitable words, right words, which somebody can accept or expect is hard to predict.
The fact that somebody doesn't want to sound pompous and obsolete doesn't mean that they ought to be considered to be an I-am-proud-of-my-tracksuit type of guy. I'm far from using hajtniesz się ze mną....very far....If I were a woman, and my husband-to-be used such a phrase, I would definitely say NO!!!. To me, the most common is "wjdziesz za mnie?"