You can actually already sleep with other survivors for better sleep, talk (kinda) and trade with them, I think you can even hug them if you get a good relashionship, I know this because of glitches on the survivor pods. (They don't follow you tho) (you can also build trust with them and all)
Also, watching a survivor die would probs bring your mental health WAY down, also they don't need to be dying, the could just i dunno, doing their own thing or sleeping, oh interacting with them would also bring your mental health up quicker of course.
Wait I would actually feel terrible if I didn't manage to save them.