WOW !! there is an issue that I CAN agree wholeheartedly with nameles and jent 1150! In this week of Tisha Be-av, surely the geulah is near !
I totally suscribe to how jwent 1150 describes it. i have been at many,many mitzvah tenz and yo ucould literally see the kedusha in the hall. I get goosepimples even now ,remembering the Bobover Rav zz’l, the Visnitzer Rebbe zz’l and others. the saying of “mi shelo ro=oh simchas beis hashoevah bejomov…’ can readily be applied to these holy mitzvah tenz.
And, namelss, you are right in saying that your “bakoshos” can be answered at that moment. This is why we drink a lechayim with the rebbe shelita before he goes to the tanz.
However, I have never heard that there are Rabbomin taht will not be “mesader kiddushin”.And, as far as different minhagim, it is like the maamer chazal, “nehorei neohrei upashtei” The mitzvah tenz are primarily a galitzianer and hungarian minhag.
( I think that Ger does not do it either)