If WOW can do it, I'm sure SE can figure out how to make this game do it as well. Also, your b) doesn't make any sense at all as the chest was already clicked on and the loot window is already in your UI.... how would the loot window also appear on a new party members UI if the chest was opened while they weren't in the party?

I want the loot window to still be there when people leave the dungeon. All they'd have to do is create a separate "instance" for the loot itself that each of the party members access during loot distribution. Again, WOW is cross server and if I roll greed and leave, I will still win the loot if my roll was the highest.