Okay bud,but what type of plot twist? Or deliberate choice?,i know it's not impossible to squeeze other sexual fantasies without them becoming completely illogical.
Not to discourage you but if by choice you mean, suddenly a girl come and ask,"hey babe i want to fuck with another guy,would you be okay with it?whatever you say i will accept"
Options: Yeah it's completely fine.
No,but maybe if i join too with him.
No, absolutely not.
Girl: okay if that's what you want.
If this is what you meant by choices,then sorry hard pass for me,not fan of wierd kink,and definitely not of possibility of any happening suddenly for absolutely no reason,whether it's optional or not,it just destroy avn theme itself.