I kinda like "other wife/other husband," because others are not quite sure if you are joking, you know?! They can interpret it any way they like but it adds a sense of lightness, since, well, legally (in most parts of this country and others) there can be no such thing
I watched that show, "Sister Wives," and I tell you I sure saw lots of potential benefits to being in a polyamorous ("unicornian"?) relationship, for sure. While I personally don't believe in the polygamy model, especially with its strictly patriarchal bias, it did really help me in thinking creatively. My 14-year old daughter loved the show too, and kept asking me if we could get a sister wife!!!
I am not bi, but aside from the sexual aspect I would LOVE to have another woman around the house, as a friend and someone to learn from and grow with. My husband is not bi, but we entertained the idea of having another man in our life, in the same way. (That didn't work out, but that's another post altogether, ha!)
As for the "UNICORN" thread topic, if either of us were bi I guess the sexual part of the relationship would just be folded in. What would be the benefit to being/having a unicorn? MORE LOVE. I can't think of anything more obvious! Maybe not simple, but it seems it would be definitely worth a try!
Also, I believe that in the pursuit of love and happiness, the main focus cannot be avoiding pain! You either let love rule your life, or fear. Mistakes in love are not necessarily a bad thing. All love is worth it, along the way, no matter how long it lasts or how it ends up. I don't regret any of the love I've had in my life, do you??