the odds are barely 50/50
Probably better if they're educated, white or Asian, not pregnant, and not super young. I don't know their demographics.
Before marrying, my husband and I discussed the circumstances in which we thought divorce was acceptable for us (abuse was one). As far as including that in the ceremony, I don't see a need.
Recently, LWers Will Ryan and Divia Melwani (now Will and Divia Eden) were married, with Eliezer Yudkowsky officiating.
I've been to 40+ weddings in my lifetime, and this was my favorite ceremony yet. Here is the video, and below is the transcript of Eliezer's... what's it called? "Blessing"?