Amk, i've been following you post and feel that I have something to finally contribute.
As to your question;
Has anyone in a monogamous relationship had polyamory suggested by a spouse and eventually decided it was for them, too? What was the journey like?
My partner and I were monogamous for the first 10 years of our relationship (minus the one time I cheated on him). We had decided that after 10 years, we were ready to try bringing a third in to our bedroom. I could tell that for the last several years, he wanted to try being more open, but I was so afraid to do it after I had cheated. Then just before the beginning of last summer, we finally had a chance to experience something with other people. We ended up spending a couple days with another male couple and then, the flood gates were open after that.
Went spent about another 6 months only sharing experiences together which was fun and I got to see sides of him that I didn't realize I would find as exciting and amazing. After 6 months, we decided to start our solo experiences. It was a very rocky first couple of months and took a LOT more communication in those few months than we ever did in the 10 years leading up, but we survived it.
After a while, i've started to see his interactions with other men as not being a threat to us and our relationship, and that's opened me up to enjoying my interactions with other men.
I think the key thing to keep in mind is that your wife's and my partner's feelings for others do not diminish their feelings for us. From what you've said here, it sounds like she still loves you VERY MUCH and she's being very honest and respectful of your feelings and is willing to do this on your terms and time table. Sounds like you're a very lucky man.
This relationship style is not for everyone and it may not be for you after all, but I certainly do applaud your willingness to learn about it and find ways to integrate it in to your ideals, it shows how much you love her.
Keep your head up! This seems to be a great community of people here and can be a wonderful support center for you in this journey!