A lot of people won't like that, because they don't want to see any girl with any guy other than the MC. But for girls like the school teachers where you don't really have a romantic relationship with them, I don't think I would mind that much. Don't get me wrong I still would prefer if the MC gets all the girls. But for those characters I wouldn't mind that much. The only characters that I would be 100% against having sharing scenes (mmf) or them being involved with other guys, are the school girls and MC's family members. The rest of the girls the mc just has casual sex with them and there aren't really any feelings involved.
Exactly that, there are so many characters, which are just "casual" interests of the MC, I can list several here, all 4 teachers (future 5), Odette, Grace, Consuela, Crystal, Tina, and several others, it may be just a personal taste, but it is interesting, other sexual relations without the MC, it makes even the characters more alive, creates a more worked personality, we know if the character is only having sex with the MC because he did something, or if the character really fucks several guys.