So technically a gamemode where you set lava to a certain level and it rises to a certain point, it comes with a OnLavaTouch event, Lava Lower, Lava Rise.
There could be a way to get it to lower back down to a certain point, maybe add an event for when a button is pushed along the way the lava is slowed down or it goes down a a bit for a while before rising again.
Winners are determined by the amount of survivors, an option to enable and disable addons would be nice, much like custom mode.