Second Partner?

My s/o and I have talked about bringing another companion into our relationship. Not on a simply sexual basis, but in an emotional mutual relationship where essentially I have a male and female to intimately bond with, and same for her, leaving my s/o with two females.
Prior to this, we did have trust issues. I have found, however that being involved in the finding, the flirting and the "game" of it all with him, has made us closer than we have ever been. Were more social and friendly in public rather than jealous and territorial. We took a lady to a party the other night and had a wonderful time and were actually hit on by a few other women throughout the night.
Obviously, I'm okay with this and so is my s/o but I was curious how many other women out there think this is normal acceptable behavior? I do want to come up with an approach to explain to friends or whatever when/if we start seeing someone openly and regularly. Would this be something you'd try with your s/o if it could work for you? Am I setting myself up for failure?