As far as I see it the best options would either be some sort of watching your player sleep and being able to wake up on command so that per hour in game equates to some returned value of rest... Another option would be to allow for 2 different instances run on a server being as if I fall asleep at night and my friend is awake he can play in the nighttime and see my character asleep and he wont be able to see me awake until he goes to sleep and joins my instance and vice versa for sleeping during night and going to day but only allow for two instances max we dont want people just sleeping 5 days ahead of their buddies and you could say if your player dies in the past instance that you die and that your play time would be the equivalent of you dreaming meaning you could be woke up from your slumbers and lose the progress you had but at least be able to try and defend yourself... idk its complex but would be a fun bit of gameplay in my opinion
