as for me, its more interesting with sharing. one-guy-rule-all is harem and its used a lot in many games already.
we have mc and old dude atm, why not be friends and gain from it instead of fight for the chick that is so teen-like and insecure behavior.
more old/fat/ugly dudes since that would make a nice contrast with the hot young girls.
also, i would like gloryhole, blindfold and similar, where the girl is unaware of mc telling another dude to participate or she believes its the mc but somehow another dude is there.
and something i think is quite rare, is mc+girl talk about doing more kinky stuff, where it takes time to convince the girl, to corrupt her mind take times.