Hi. I'm the wife. This is my new account.
1. When he says we are happy with the relationship, I think he really means that we're happy with one another, and aren't looking for a person to double as duct tape. But really, expecting no relationship to change is I think a bit silly. Relationships, even traditional mono ones, are going to change, and its not something to fear just a fact of life. We just don't need her to fix our current mess. I'll hire a marriage counselor for that.
2. When I say I am uncomfortable with being a hinge, I think the kicker is twofold: One, I am worried about being able to competently divide attention between both parties fairly particularly since my husband enjoys spending a lot of time with me, and I enjoy spending a lot of time with those I am involved with and I would imagine anyone I click with would be the same. Dating the same person won't fix that, but I wondered if it would lessen one person feeling left out.
I am also concerned that starting off with a 'Vee' in the hopes of a triad. Somehow just feels disingenuous to everyone involved at the moment. That there will always be this pressure to either find my husband attractive or find me attractive when that wasn't quite what was advertised. So, probably thinking not the best idea in the world until I get a better handle on either how to politely indicate that I want something closed, and long-term or using a different approach as others have suggested and let things work out and be more open to alternatives. Also learning better time management skills and knowing how to make sure both people feel special and not ignored.
3. Immediate exclusivity when dating? Yes, but not for the reasons you might imagine. Before I was married, I expected the same from my partners with whom I made clear that I was looking for something long-term, just how I personally choose to date. You young people and your new-fangled ways! Through I will admit, I had not considered that a safe base for the other woman would be quite important when embarking on a relationship where she does not have the power, no matter how unintentional or unwanted as that might be by all parties. I could see how that might be attractive, or even necessary.
I can definitely respect someone for wanting to date in another way for whatever reason they desire. However, I would worry about feeling like I was competing with the other dates to try to capture her interest and her heart if I liked her. This is to say, I do not think I have such a good handle on such things to the point that it would be irresponsible or immature to willingly get into such an arrangement. I don't think this is entirely fair to her or her other partners, and doubly, if not triply so for a husband or other long-term partner.
Perhaps holding off until we both feel comfortable with other arrangements might be wise, to consider that anyone one of us clicks with might not click with the both of us and definitely would not wish to feel trapped or forced. I thank everyone for commenting upon this, in particular AnnabelMore. It certainly helped to understand the situation from the so-called 'third' point of view, and how they might, sadly, be treated as such. We want to share and find someone special, not control nor objectify another person.
4. If it makes anyone feel any better, I had to read a comment a few times to understand there was a TV show regarding this since I am so out of the loop that the loop and I reside in different dimensions. Reminds me of a bit of when a movie features an animal so everyone rushes out to buy one.
And sorry if this post seems argumentative or flippant of advice--I am really looking not to the 'what' of what not to do but the why to really understand how best to approach this as to cause as little drama or offense to others, as well as to understand the issues at hand.