nah. mc's gf is just fine, she is not just used enough by other survivors
I would be ok with just gf and Hyuna(?) as heroines tbh, I think allowing the MC to cheat on his gf and have that choice be a consequence later on down the line of one of the story branches to be a cool way to punish the player and lead to a bad end where otherwise MC could potentially redeem his relationship with the gf.
This needn't be the case in every story branch, perhaps just one of them.
3 heroines is already too much, nothing of value is really added by adding quantity of choices rather than focusing on quality. Most people that watch and play NTR games are men looking at the female cheating element - I doubt many people care at all about the male cheating side of things, so all of these heroines besides Hyuna imo are wasted development.