What if a partner enjoys moresomes - whose will will prevail?
Say he is happy to indulge your desire for triple penetration, wouldn't it be only fair to indulge his desire for two ladies at once, even with no inter female activity. Or would you be happy for him to indulge his pleasures elsewhere?
I know some women who rate themselves 100% straight and have done FMF for that reason and enjoyed it - certainly they spoke about in a positive way and didn't rule out doing it again.
I do think you get in to dangerous territory if you start saying I'll FMF for you if you MFM for me - because you are potentially asking someone to do something they are not comfortable with and that's never sexy. If a guy doesn't feel it is fair to MFM for his female partner without her FMF for him then he shouldn't MFM - if he wants to for his own reasons then that is different. But you can't 'buy' consent for a sexual act with another sexual act.
I'd like to MFM but my man would not be comfortable, I know that and I would not try talking him into doing it because it wouldn't be fun for ME if he couldn't enjoy it on some level. I'd also maybe like to FFM for my own reasons - he'd be OK with that and would enjoy it for his own reasons (unsurprising) - but neither of us would feel he owed me anything for that. That's not how sex should work. It should be about mutual pleasure.
If a guy does MMF/MFM because his woman has asked him to that's one thing. It does not imply consent to anything else. Likewise if a woman FMF/FFMs for her guy that's a seperate thing too. If a guy NEEDS FFM/FMF for sexual gratification then he needs to find a partner who's happy with that.
Yes - sex is give and take - but how can you be OK with trying to coerce your partner into something they are not turned on by? For me that's just not sexy.
The question of one partner going elsewhere to find gratification is a separate one. Some relationships can work that way, others cannot. Not wanting to make gender an issue I'll put it this way; if partner A cannot fully satisfy the sexual needs of partner B, but partner A's needs are met, then there is a problem but it does not automatically mean that partner B has the right to seek satisfaction elsewhere. They need to sit down and find a compromise that does work... if there is none then maybe the relationship can't work.