I assume by "a" whitelist/blacklist, you mean "the" whitelist/blacklist, in which case the message the user receives while dead would not be controllable, it'd be, "you can't log into this server" or "you are banned" rather than "you are dead". I wouldn't be able to tell the user how long they have left. I also would have to check the entire death list very frequently to clear living players off it- depending on how large the server is, that's a lot of wasted CPU cycles for something that's constant-time to check on login. It seems like a lot of downsides, especially since there are other systems that might take advantage of similar functionality.