We’ve all suffered the frustration of leavers but I don’t agree with your suggestions.
As other have said there is no easy solution for this and Blizzard aren’t going to add any kind of negative data to the mix. Certainly not any exclusion from loot. That’s on par with getting a game ban tbh, something only GMs should be able to do.
I am not a fan of commendations myself it’s kind of useless information, it’s just a form of ‘like-farming’.
I don’t really want to end up with players afking until their punishment time is over. You’d also catch a lot of people in the crossfire with blanket rules like that. When I play with friends we will often try a key decide we’ve messed it up horrifically, and just leave and do some other key. Nobody should be punished. Also who is the one getting punished, do leaders just sacrifice someone and boot them out. They take the hit and the rest are okay?