As a threat, Jeremy is a wannabe player that can't really hook up with anyone unless you let him.
Uhh regardless of the player's choice at the first dance club, Jeremy Fucks. It's either Allison or Emma based on choice, but in the end, he fucks. Is it because he's so miraculously charming and tells great stories and is the life of the party? Hmmmm. Or is it because he has the magical bbc bully plot armor?
Fundamentally, this isnt even a consideration with the women - they do have partners that screw around on them, but we really don't care because they all have an abundance mentality- for good reason. If Lena gets rejected by Ian, we don't care because we have Robert (as much as he sux), Axel, Mike, Mark, Jeremy, Holly, Ivy, Louise, [holy shit im typing a long list] etc as options.
I think a lot of people wouldn't feel bad about this inequity if Ian had, for lack of a more polite term, a group of side pieces; girls seperate from the group and their spheres of influence, like he could find the equivalent to robert/mark/mike for Lena in the bar some night. He doesn't though, and all his options can be poached - which is why playing Ian always feels like playing defense. Furthermore, the game restricts certain actions to a greater degree with Ian than Lena - they can choose to be in a love relationship, and Lena STILL has the option in ch9/ch10 to mess around with mark/mike, whereas Ian's options with other girls are severely restricted - (as in, it forcibly breaks up you with Alison if you choose to date Lena). I just want some damn consistency- if one protagonist can screw around after the relationship start, why can't the other? Or why can't neither?