All the issues that I have heard above from the females perspective, fear of attachment, negative body perceptions, performance anxiety and concerns about husband becoming jealous can all be addressed from my past experience by being patient and using that time to develop a relationship with the guy online, over the phone, and in person for an "understood to be platonic only meeting" to get to know one another better. Once you are familiar with a person the insecurities should go away if there is chemistry between everyone. Now this person isn't an unknown an longer, but someone that is real flesh and blood, which puts most people at ease for possible disrespect after getting to know them. If you have the right person then that person should be someone who is forgiving, understanding and wouldn't think to insult or criticize another person during an encounter. If they did you need to work on your picking process, because it is flawed.
Now the objection from women that a MFM 3some is just a trojan horse of their guy to sneak in an eventual sexual encounter with another woman, is more nuanced. It requires the man to communicate effectively with his wife/girlfriend/partner/cohab to express his excitement and arousal at the idea in the most animated emotional intensity as he can manage. Repeat often, or some variation, "It would be the most incredible sexual experience of my life if I could watch you have sex with someone else. I would be over the moon because I think you are the most beautiful woman in the world. I have no interest in another woman, I have you." I threw in "If I had pictures of you having sex with someone else I wouldn't want to look at pornography of other women, because your pictures will be the most erotic pictures I could ever imagine. I fantasize about watching you have sex all the time. I can't get it out of my mind" This quote is what my wife told me convinced her to give the lifestyle a try. She knew swapping with couples was part of my request, but my viewing of porn of other women made her feel inadequate (lifestyle teaches you about your partner) and truthfully I almost exclusively only looked her pictures and videos for over a decade.
Next advice is don't be embarrassed about your kink, preference, whatever you want to call it. I have had stories told to me of guys so worried their wife will think they are weird they mumble and garble words so she misunderstands what they are trying to say giving her the idea that they want some kind of trolling motor for a boat (true story). Trust me I've heard some funny stories, from wives chronicling their husbands presentation when he tried to ask about the lifestyle. Recaps of the confusion coming out of nervous guys trying to explain they want to watch their woman have sex with someone else mixed with the interplay of their loving bride who is trying hard to understand whatever language their husband is now speaking, are belly laughingly hilarious.
I have 2 suggestions; 1) Get over your worry that she is going to think you are some kind of weirdo. I say this because she is going to think you are weird with this request, especially if this is out of the blue with no previous mention of the subject. So there really is no point in speaking low and softly while you nervously trip over your words as if this is somehow going to make this less weird. It will not trust me. My second suggestion is 2) Really practice before you go on stage rather than winging it. Treat it like it is a speech you are giving in front of a crowd when preparing and you will do much better and speed the process along rather than slow it down. I mean you need to look at it from her point of view. She has this nervous guy speaking in fragmented sentences quieter than she has ever heard him speak before, while you are trying to figure out how to ask her about doing this for you in a way that downplays your embarrassment over wanting this kink.
A bonus suggestion is I highly recommend not doing a cold open, but actually start broaching the subject in the bedroom in snippets so you don't just hit her out of left field. Most women can't believe a guy would want to watch his wife/girlfriend/cohab/partner have sex with someone else. This usually goes against everything a woman has learned, over a lifetime, about how men feel on the subject of their woman having sex with another man. That's why almost universally a woman's first thought is that their guy has to have some ulterior motive. The most common is "you want to fuck other women", then "you don't love me because you wouldn't want me doing that with someone else otherwise", the ever funny "you're trying to get rid of me" and bunch of others. Easing into it over a few weeks can give you an idea of her objections beforehand so you can be prepared to answer those objections.
One final thing I forgot to add is to ask questions rather than assuming how she is feeling and what she is thinking about this so you actually answer her question or concern, rather than the one you assume is her question. I have learned from my own spectacular failures in communicating with partners that when I try to read their mind by assuming I know, I really don't know what she is thinking. It's best in my experience to not test out your telepathy skills by just asking her. Not listening is a surefire way to fall down out of the gate by making her feel uncomfortable because in her mind, you aren't hearing her concerns about this confusing bizarre sex play idea. They typically are somewhat apprehensive already and then not listening will throw them into full-fledged panic as they conjure up visions of you coercing them in all sorts of uncomfortable ways. I have learned having done this with at least 3 different women, that asking them "What they think about it", "Can you think of a scenario doing this that would excite you" and other questions soliciting their concerns, opinions and feelings will get you a lot further and is more likely to be successful. Not bad for your relationship either to improve your listening skills.
Summarizing it all, when having this discussion with your wife the best way to communicate with her is to view this from her perspective, actually listen to her questions and concerns, prepare so you aren't nervous and come across clearly, and last but not least, seduce her by being your genuine self that loves and cares for her. Of course you need to remember to prepare, prepare, prepare. Don't skip this step. Do some self-care work on accepting your desire, if that is an issue for you, so that you come across confidently and clearly when you're discussing this with her. Emotions tend to have a bigger influence on women than us men, so if you are unsure about this being acceptable, you are going to transfer that feeling of doubt to her. My recommendation on learning to accept your fetish (loud and proud baby) is to put it into perspective. It may be not be vanilla, but it ain't the weirdest kink out there either by a wide margin. Plus remember there are some intriguing benefits for the woman too, which should start percolating in her mind as the discussion continues.
Using these suggestions doesn't guarantee success, because it is important to accept that there are legitimate reasons for someone not wanting to become involved in the lifestyle that you will not be able to be overcome, nor should you want to overcome them. If this is the case then this is the point where you have a bigger self-evaluation on the trade-offs and priorities you need to have a happy life. Excluding these dead stops, this formula has worked for me with partners of mine who all really enjoyed being a hotwife/hotgirlfriend and were happy with their decision. I hope this helps and good luck.
