This is pretty late for replies, but I've also made the fun mistake of spilling fantasies while drinking with the wife.
In my case, I found that we both loosen up a bit when we have a couple of drinks on the porch and just talk. She's much more open to kink and suggestive ideas and she morphs into a pretty damn good dominant when she's got some liquid courage in her. That being said, she's normally shy and reserved, uncertain and suffers low self-esteem when sober, which makes her uncomfortable with discussing fetishes (sober), and less likely to consider or discuss doing these things.
You should probably plan out a next steps, such as intentionally setting aside time to drink again together. Don't get sloppy drunk, just a good buzz, then bring up the topic again. Keep it playful and positive, and also sensual and exciting in how you bring it up. If she doesn't take it well, at least you can blame alcohol the next day.
From what you've said, it seems like she may be open to the idea, but you need to be really careful about TMI. Don't go full-kink even while drunk, maintain control over softly and gently pulling her into the idea. For instance, the concept of her being with someone else is the 'idea', the specifics like you joining in, cleanup, chastity, etc.. are just that - specifics and kink. When the idea festers in her mind, she will fantasize it with her own ideas, and probably already has.
A good example is that when my wife fantasized about it, she saw it as just her and the other guy going on a date, getting a room, etc. I wasn't part of the equation. My fantasy was to be in the hotel room, and then watching and/or participating. This made her uncomfortable and I've read here that a lot of wives want to start without their husbands being directly involved, which is a more comfortable starting point for many women. So keep it vague and be ready to hear what she would want from it and understand that it may not align with what you want from it. Take it one step at a time, I can't stress that enough.