Rabbi Kornfeld:
A few thoughts on the folowing topic:
(From Insights to Yoma 13:)
Rebbi Akiva Eiger adds that a Chupah cannot be performed at this point for an additional reason. The Gemara (Kesuvos 56a) discusses whether a Chupah which is not fit to be consummated with Bi'ah is a valid Chupah or not. The RAMBAM (Hilchos Ishus 10:2) rules that it is not a valid Chupah. Thus, a Chupah done on Yom Kipur is not valid since Bi'ah is forbidden on Yom Kipur, and the Chupah is not fit for Bi'ah. Even according to those who do not rule Halachically like the Rambam, and prohibit such a Chupah, our Gemara might be trying to avoid the issue of making such a Chupah because of the doubt cast on it in Kesuvos.
According to the RAMBAM the Kohel Gadol could be appointed a ketanah who may not require a chupah hara'oy l'biah and is married enough with the consent of the father. (B'derech Efsher). (this also would answer the question on him of how the nisuin takes effect right away when shluchim are sent eventhough it's not ra'oy l'biah)
Your thoughts back are appreciated.
Shimmy Messing
Good question. It would seem, though, that marrying a Ketanah by way of consent of the father only works when a Ma'aseh Nisu'in is done, i.e. a valid Chupah. A Ketanah (older than the age of 3) is Re'uyah l'Bi'ah (Nidah 44b), and therefore the Chupah must be fit for Bi'ah (which on Yom Kipur it is not). Even if her father gives her over to a man without her consent, nevertheless the marriage is only valid if she is Re'uyah l'Bi'ah, for otherwise it is not called a "Chupah" at all.
Giving her over to Sheluchei ha'Ba'al works only when the woman is Re'uyah l'Bi'ah, but the only obstacle is the distance between them. (This would imply that according to the Rambam, who holds that Chupah with a woman who is a Nidah is not considered a Chupah which is fit for Bi'ah, giving over a woman who is a Nidah to the Sheluchei ha'Ba'al would not be a valid marriage because she is not Re'uyah l'Bi'ah.)
M. Kornfeld