Standing for the Chosson and Kallah at a Wedding

What is the origin of the practice to stand for a chosson and kallah at their wedding? The topic recently came up on a discussion list that I subscribe to, and the following has been pieced together from that discussion and other archived discussions found using Google.

One reason often given is because "chosson domeh l'melech", that a groom is compared to a king. The source for this is the end of Pirkei d'Rabbi Eliezer, chapter 16, which states:

"A groom is similar to a king. Just as a king does not go out in public alone, so, too, a groom does not go out in public alone. Just as a king wears garments of honor, so, too, does a groom wear garments of honor during the seven days of rejoicing. Just like everyone praises a king, so, too, everyone praises a groom during the seven days of rejoicing. Just like the king's face shines like the sun, so, too, does a groom's face shine like the sun, as it says (Tehillim 19): 'He made a tent with them (the heavens) for the sun, which is like a groom going forth from his canopy'."

A rebbe of mine noted that this axiom is only said regarding a groom, though - and moreso, there is no halachic concept of a queen who can demand the same level of honor and awe that a king can (as described in the 2nd perek of Sanhedrin). This being the case, he argued that the parallel custom to stand for a bride has no basis.

Another reason often given is based on Bikkurim 3:3, which states that the craftsmen of Yerushalayim would stop their work and stand to greet the people who were bringing Bikkurim. In the Yerushalmi, R' Yosei b"r Bun states that the reason for showing them this honor is because they are going to do a mitzvah. This idea may also be the reason why we stand at Vayevarech David, due to the practice of giving tzedaka at that point during davening, but I'm not sure if there are any other situations where we stand for those who are going to do a mitzvah. The mitzvah involved would presumably be p'ru ur'vu, as I don't believe that marriage itself constitutes a mitzvah. This being the case, the practice would, again, apply only to a chosson, as the kallah doesn't have a mitzvah of p'ru ur'vu.

One poster noted that thirty years ago, no one stood for the chosson (or kallah), which may mean that it's a new practice altogether. Another poster observed that in Europe, the minhag was always to stand for the entire chuppah (and, indeed, some say that one is m'chuyav to stand for the entire sheva brachos under the chuppah, either as a din of kavod la-melech or because the nisu'in are considered to be a davar she-bikdusha, similar to Borchu, Kaddish, and Kedusha, which all require standing, so that the question of when to stand and when to sit never came up, further evidence that this may be a minhag amerika'i

Regardless of the validity of and reason behind the practice to stand for the chosson and kallah, it should be noted that there is a mitzvah d'oraisa to stand for the elderly (mipnei seivah takum), so that the people who are sitting along the aisle should *certainly* stand when the grandparents of the chosson and kallah pass within 4 amos of them in circles where the practice is for them to walk down the aisle (assuming that they are, indeed, above the age of 70).

Update, 8/12: The excerpt from R' Zev Cinamon's new sefer "BeYom Chasunaso" cited by Chaim B. in a comment, scanned by Dr. Yitzchak Levine. Sounds like a fascinating sefer.