Here's my take.
You could say that I'm a unicorn. I'm a hot (I'd like to think) bi chick without a primary partner who actually has a huge thing for couples (honestly, people often seem to find this a little odd but I greatly get off on the energy between long established partners).
I recently redid my OKCupid profile because I wanted to consider dating again and, in the course of doing that, I looked at a lot of other people's profiles. I found a few very interesting looking people, but then crossed them off my list immediately. I will never message them.
Why? because it's clear that theywere unicorn hunters -- halves of couples that think of themselves as a package deal and are looking to add/grow/find someone to join their relationship (what does that even mean... wouldn't we be forming new relationships, not just "expanding" an old one?).
I refuse to enter a situation where if I'm interested in a person (a serendipitous enough occurrence) I'll the expected to get involved with another person. No way am I down for that sort of expectation or pressure. Gross. Not to mention the millions of incredibly unpleasant and dysfunctional unicorn hunting stories I've read here... it's just not a functional or healthy paradigm.
On the other hand, I'm meeting a lovely guy I met on OKC this coming Monday. Hopefully sparks will fly.
He has a partner already, he told me she's been gleefully teasing him about his excitement over me. Frankly, she sounds like my kind of gal! Maybe down the line I might even want to get to know her better too. But, if there had been some sort of implication that that was being sought or expected, I never would have messaged him in the first place. It'll happen if it ends up being right for all three of us when/if I get to know her, but it won't be a cloud of "one of us or neither of us" over my head until then.
All of this is to say, I think you are going about things the wrong way. Maybe if you release your expectations for a certain configuration you'll find wonderful experiences that are more free form and, who knows, maybe even unexpectedly become what you originally were seeking (but don't count on it... that's the key!!).