I'm not sure anyone has attempted this, but it would be pretty neat to have a plugin that gives people doses of radiation when they head outside into open air! Something a bit like the vampire plugin where vampires are damaged by sunlight... but if possible also including the night air. Just a suggestion at any rate! The idea is pretty obvious: a post apocalyptic world! Bonuses may be to set all tree's on fire as well or something of that sort... something to make the whole mining part of Minecraft more fun!
Well I don't know how the damage would be done outside, as (IIRC) the vampire plugin runs off of light and not absence of it. If you were to do any light light, you would constantly take damage. As for the tree, that might make the server lag...
Hmm, possibly using a check to see if there is any blocks above the player. But that wouldn't help sidewaysness.
reminds me of metro2033, i support this idea: to not lag the server much, you could set a specific level? so everything above.. 64 = die. but thats bad then :/ no outposts and such
And there are some pretty big mountains above 64 on some servers.I cant think of any viable way of doing this.