At the top of the list would be to watch her in a mfm. We have had many but this would be without me being one of the 2 men.
I would also want her to have a dominate boyfriend who enjoys being rough with her.
We have never done a GM. I like the idea of this. I have a fantasy where my wife and a steady boyfriend have a "wedding/commitment ceremony." I give the bride away and they exchange rings before their honeymoon starts.
We both love it when she and her lover have an emotional connection. It makes the sex that much better for her and therefore better for him. She would do almost anything sexually for a steady boyfriend, not so much with a fuck buddy.
If I don't go with them (about half the time), I stay home and look at pics and videos of my wife while I chat to others online about what's happening.