Bdell - I have not read the other responses as I have seen the RA create a lot of intense emotions on both sides of the fence here before. I know you are hurting and I want to help you deal with that.
That being said, I am not going to tell you what to do, but I can tell you what you are pondering is pretty normal thought process a lot of BHs go through. Myself included.
The unfairness gets to you. This is unfair in a society that pushes "fairness" to a fault. (e.g.- See everybody gets a trophy athletics) What our W did, for whatever reason, was cruel, unfair and hurt you in places you did know you had.
One of the usual ways this plays out in your head is that if you got to experience the "fun side," of this crap (as you already are on the bad end). It is part curiosity, part revenge and part desperate attempt to feel better. I get it, I have been there myself. You just want this agony to stop and you start looking at any and all things. Alcohol, hobbies, RAs, whatever.
I understand how hypocritical it is for a WS to ask that their BS be faithful, "now." After all, had we known that we were living in a one sided open M we may have decided to pursue other partners too. We never considered it before and Dday has made that possibility real for us. I mean our WWs risked a lot to pursue these relationships, there had to something they got out of it, right ? Hindsight is 20/20 and looking at something with the full consequences in place sometimes hides the short term benefits the WS received from it. Are the longer term consequences to our WW, US, the M worse than any benefit ? Of course they are. My point is this RA rolling around in your head could be a step toward empathizing or understand the why for your W. You can try, but you'd be the first BH to get that one figured out.
Your Ws actions do not reflect on you. They reflect on her. She has certainly screwed up your life and you will never be the same, but at some point you will realize that most of the "fault," lies outside of you and you bear no responsibility for your W's choices. BTW Being "changed" does not necessarily mean worse, it just means diffeent. It can also mean being better, wiser, stronger and less naive (not calling you that just making a point).
You have to think about the man you are and what you can live with. This could feel great now, but who knows how you will feel about it later on. After all you can't go back and change the past.
I know you will think on it before leaping, just think out all the angles. Ask your W about how she felt and feels about it then and now.
At the end of the day this is really about trying fill a need you have and there maybe alternatives that could have fewer side effects in the long run.
Sometimes you have to think on the thought for awhile to really understand what is behind it. For example you may think this is way to help your W understand how you feel. There are easier ways to do it. Telling her and showing her how much this has hurt you transfers the ownership back to her. She didn't mess up your life, she messed up her life. You have the same choices you always have had and can lead whatever life you want to live.
Anyway, I am not saying you should or shouldn't. Just think on it for awhile. I would suspect you aren't sure of the answer either and this will have consequences no matter what direction you take. All choices do.
PM me if you want to.