I Want My Wife To Be Submissive

I guess this is also more of me seeking advice more than a confession. But my wife and I have been married for 6 years, together for 12. When it comes to being sexual we were super vanilla at first. We fucked about 4 times a week and we have had many great experiences together. We slowly realized we wanted to also include other people so we have an ENM relationship now and we have had multiple foursomes, threesomes and even went to a sex club once. We still do this on occasion but ever since we had our second kid her sex drive is almost non existent. So we had always talked about doing more BDSM type things and she does enjoy pain from time to time. Typically she is the more dominant one in our relationship but I have been having a very deep fantasy lately, so much that I’ve had dreams about it. I want her to be my sub, I really wanna dom her properly. Like I come home and she’s on her knees and wearing leather and a collar type stuff. That type of sub dom relationship. This is so not her personality and I just don’t know how to approach it or even figure out if she’s interested in that. Her sex drive being so low lately I just don’t know what to do. Maybe this fantasy will just remain that. Any tips would help fellas.