All you need to do is remove all content from the game, excluding guns, melee, mining bots etc. and throw everyone in a huge free for all spar arena that gets smaller and smaller in timed intervals. There would be rock and wooden structures, which could be destroyed by bots for resources, which would be used to build shelters that defend you from other players. The last man surviving wins, and then it starts over.
Oh, and change the name of the server to something cooler