Doesn't it increase the clip size? And improve the weapon sway?
I didn't even consider this a thing. I don't mind if a teammate executes a foe I downed, and I'll execute someone somebody else has downed. As long as they are being executed, I don't really think it matters. If someone executes an enemy they didn't down, they are working within the team. Playing support isn't being any more of the 'team player' than being the person who viciously hunts every downed player.
I've only disconnected once, and that was because my connection died. And yes, you can be fucked over if you join a match late while having a mission. Really your objective should be to complete the mission in 2 days anyway, rather than 3. That way you can be screwed over once and still manage.
It isn't perfectly thought out. Missions aren't thought out with both game types in mind, which is strange seeing as they only have two to balance for. Reaching a high amount of downs in Survivors is more difficult than in Supply Raid. Alternatively, you have more chances to complete a required amount of shiv executions in Supply Raid. It's murky, yes, but certainly serviceable.