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But brothers and others is assur
If they (men & Kallah) are not touching, then why would there be a difference. I don’t think there is one.
If they are, I believe you are correct, even though there is no Issur of Negiyah. (It is somehwere up there, I can’t remember the source offhand).
The Groom is a Dav’ar Mechuar and shows off what will be later, and I would imagine that the Rabbonim would frown on such a practice.