@Magdlyn I don't think I want to do an entire other separate relationship though I definitely desire more of a group relationship. Ideally someone that comes over and hangs out with us a few times a week or something.
I hear that you fantasize about sharing a lover with your wife. This person would somehow like very much or love you both equally, and desire sex with both of you equally. And you would both like and desire her equally. Honestly, your fantasy about what poly is, is the most common one out there, with formerly mono couples. You're used to sharing your lives, so of course you'd want to share a person. This idea about what poly is, a straight guy with 2 bisexual women, is the most common fantasy of males. That's why it sells in mainstream media, in porn videos, etc.
But your hypothetical unicorn would be a real person with tastes, desires and preferences of her own. If you do a search here on triads, you will find everything that can and does go wrong when a couple goes unicorn hunting. Here are a few examples.
What happens if you (personally) really like someone, and she seems like you both a lot, but wife doesn't like her much? Or what happens if the unicorn seems to like both of you at first, but then loses interest in one or the other of you? Say you and she like each other, are insanely attracted to each other, but after a few weeks, the wife is feeling meh about her? Can she veto your new relationship and break both your hearts? ("We're supposed to be sharing her!") This could lead to resentment on your part. Good chemistry and/or love comes along rarely in life. How would it feel to lose a new love for the sake of your wife's fear of your loss?
What if the women desire each other, and you desire new gf, but the threesomes feel awkward? Threesome sex is tricky. Many people find it stressful, because you all have to cooperate to make sure everyone's needs are met. Sometimes in the heat of the moment, 2 people start going at it and the third person is left to watch resentfully.
The women might want to continue in a sexual relationship (your wife being very excited to explore her bi side) but maybe they really don't want you in bed with them most of the time. Maybe the woman will even want to rope wife off for her own.
Would you let the women go at it and then seek a partner of you own? Or would you force your wife to break up with the new woman until you find a a woman who will love you both equally and vice versa? Lather, rinse, repeat?
Or maybe the woman will want to rope you off for her own. (Most people don't understand polyamory.) And this could not only fill your wife with envy and jealousy and fear, it could even lead to divorce.
What woman is going to have free time to come over and hang out with you and wife several times a week? Does she have a job, school, kids, a boyfriend or girlfriend of her own, hobbies, platonic friends, an ailing parent, perhaps? Or is she somehow just free at your beck and call any old time, whenever you and wife have an evening free?
I'm not saying it's bad to have fantasies and dreams. We all have them. But some unicorn hunters hunt for years, having one relationship after another last a few weeks or months only to end in jealousies, envy and distrust. Many former unicorns get very hurt and after a couple of tries, back away from the idea of finding that perfect couple, a straight guy and a bi woman in one tidy package, who will provide her with pussy and cock all at once. The thing is, couples have a shared history that puts a new lover at a disadvantage, and often feel "couple privilege," putting their needs, rules and boundaries out there as the first priority.
Some unicorns are women with low self esteem who are people pleasers, and they end up getting abused by a couple, almost made into a slave, with few rights of her own, made to do chores and childcare for the couple, but are hidden from the public eye. They can't go to a public place and be recognized as an equal partner, or go to birthday parties, or spend an actual full holiday with her bf and gf.
Now, Vs are extremely common. In a V, you might be the hinge. You'd have a wife and a gf. But the women would be metamours. They might meet. They might not. (Your gf might not want to meet your wife.) If they do meet, they might become friends (or not). They might stay acquaintances. They might end up lovers. While this is extremely rare, it is the only ethical way for a triad to happen. It's not fair to set up a relationship shape, a triad, and expect to find a person to fill that role (shared lover). In polyamory, the people come first, the relationship shape second, as it suits them.
Here is an article from a secondary's POV. What are her rights and expectations?
https://www.morethantwo.com/polyforsecondaries.html