I do think this would be a pretty cool feature to have but not for these reasons. Like
@JustNathie said, these bugs are not permanent and will be fixed eventually. However, this feature could be useful to players who may have to rejoin the game for whatever the reason may be. Some users may crash or some mobile users may accidently close their game. (I'm not mobile and haven't played with a mobile device in a fairly long time so I'm not sure how often that happens but I assume it's fairly annoy to some mobile players).
Well, I don't think Cubecraft would make such a command and not have solutions for problems like this. A simple way of dealing with this is by adding some sort villager NPC whenever someone disconnects, allowing other players to kill that NPC while they are disconnected and counting it as a death to disconnected player. While the player is disconnected, there should be a time limit of 1-2 minutes which seems pretty reasonable for a game like EggWars and I believe it would also be a great idea if the player would be eliminated from the game if their egg is broken while they are disconnected. I'm not going to cover all of the problems that can come with this a command like this but there are solutions to
your problem with the command :D
Overall, I think the command is a great idea but I also don't think it's needed right now, maybe in the future if enough players request a feature like this. Most bugs are currently being fixed and a command like this is a pretty low priority ^^
(just my silly opinion!!)