Good question and one I've been dealing with since I decided to start coming to terms with myself.
Ideally, I would have my husband and my gf who would also love eachother deeply but not be sexual. I suppose a mono lesbian or poly bi woman with her own male life partner? She (or they) would be completely integrated into our family and us in theirs and the relationships formed would be, at least sexually, closed. There's always room for more love and friends.
But...there's room for change. When with P I had that for a time. But she's also bi and had a male partner (who was a huge part of the problems leading to the end). I was willing to open the relationship to a triad in order to fulfill her needs emotionally and sexually as a bisexual. N and I discussed it as well as moving her in with us if it came to that point. She was also so close with my son. It didn't work out that way.
I suppose I have an "ideal" but the end result would depend on the person(s) eventually involved, should we ever venture forth and try again.