This is one thing I've specially heard would be useful (and I think it's very easy to make): Each player has a custom spawn where they are warped when they die, rather than the default spawn. This custom spawn would default to the server's spawn point. If the server's spawn point was later moved, the custom spawn point would remain. Existing players would continue to spawn at their original spawn point, while any new players would spawn at the new server spawn point. The spawn point could then be moved again, without affecting where any existing players spawn. Players would be able to /migrate, which would update their custom spawn to the server's spawn. Some servers may also enable players full control to set their own spawn.