So many people are saying they'd leave if the FMC has sex, but I for one would be playing only the female side.
The fact there's not NTR and you can play each character individually and understand the story means the MMC and FMC likely have their own set of LI's to pursue, if the FMC indeed has any at all. IF -- and only IF -- they (for some reason) so share the same LI's, the fact there's no NTR being claimed means the sex is completely seperate from the main story and if you romance the same girls with both characters they'll not acknowledge they're with the other MC and no 'conflict' will come from it.
All this means that the people that don't want to play a FMC won't have to touch their side of the story at all, even to steer them clear of sex. Otherwise, sex scenes with them probably would be more like "NPC" sex than sex you chose for them. I guess that would still turn off people who want their male charactter to be the only male to get sex, but eh. Can't please everyone anyway.