I'd like a more punishing system for damaging and/or killing teammates in PvE atleast. I mostly play hardcore and 9 out of 10 times I'm killed by teammates. most if not all of it is accidental, sure, I have my ''oh sh*t, gotta empty a mag in this moving thing that just breached into a room'' moments too but overall I have a pretty good awareness of where my teammates are at. I often wait for my team to move forward before me because I KNOW certain situations will get me killed by teammates.
And again, I know most of it is accidental but putting a more severe punishing system in place may help some players be more wary of where their teammates are at, otherwise they'd have to wait out... say, 2 objectives before he/she can respawn. I don't know what but it should be something that makes you really not want to hit teammates