My wife before she passed away, had put me in that situation years ago. She found it to be extremely exciting to watch.
I had a one time cock sucker whose husband was dying and he wanted a threesome with another woman. She, at that time, wasn't into women but she agreed so long as she could find a boyfriend later and have a threesome with two men AND she wanted him to suck cock. I've always been turned on thinking of that scenario.
Sucking cock at the request of a woman is awesome, love being with a bi couple and indulging them both.
Kind of a long story that I posted on other sub threads, so I will try to keep this more brief. Way back late in high school and early college, me and my neighbor were pretty frequent SBs. of course women became available shortly thereafter, so that was the end of that. I never told anyone else about it, especially my subsequent female partners, ex-wife etc. when I was just starting to date my current wife, we did the usual sex talks. She confessed her history and fantasies, of which I had a lot of the same. She had never been with another woman, but fantasized about it. COOL! Then she asked me if I had ever been with another guy??? OH SH*T. so I told her. And initially she was pretty shocked, and I thought she might break it off. Eventually the idea kind of grew on her, to the point that we started watching bi porn together. it always got her worked up. we eventually got into MFMs with the same friend, while at the same time getting into anal and pegging. She really played the role as a guy with a c*ck. She would have me suck it, and then f*ck me, always commenting that she bet a real c*ck would be so much better. SHE suggested looking for a bi guy. She wanted to see me doing the real thing! we started looking around, but unfortunately had no luck finding the right bi guy. I’m curious how she would’ve reacted watching me suck another guy, or have him top me. Water under the bridge.