Never had that situation, but as I have posted, inadvertently I became a switch with a young Mistress years ago. I was in my mid 40s and she was in her mid to late 20s and often switch roles in session, usually with her topping at the end. The age factor was part of it and we loved it, but it was just the two of us.
In my current situation with my longtime Mistress who is a few years younger than me, I’m in such deep subspace with her, if she wanted me to watch I’d say yes. But if I thought she was, let’s say uncomfortable in the middle of it, I’d become very highly protective. (And I’m being diplomatic in my words.) In reality I doubt it would ever happen. My Mistress is so Alpha she would never consider such a thing. She’s so aggressive sometimes when I’m in a high state of arousal with her, she says she would use me to entertain a couple of girlfriends or take me to a glory hole. It’s all talk… I think. LOL!