My Havruta and I were learning Hilchot Shabbat in Zichru Torat Moshe [ZTM] and Q'hilat Yom Tov [QYT]
In siman 52 on Miqach v'mimkar the QYT 1 states - and we do not do Qiddushin on Shabbat
Then comes policy
There is a famous t'shuva of Rema [number not available now] about an extraordinary case when the Rema made an exception.
Several criteria were elaborated to provide that exception.
The final line
"P'shita" that we should be cautious at the outset to avoid this situation - quoting Hayei Adam [same author as ZTM]
AFAIK, the Rema himself prohibited weddings on erev Shabbat and YT
And now we can summarize
No Qiddushin on Shabbat
• Policy: No Weddings before Shabbat or YT lest it extend into Shabbat
IR A harchaqah as a result of an incident - a maaseh shehayah.