I think it would be really cool if you could build something like a custom skyblock, parkour, or pvp arena and invite people to play it in survival/adventure mode. I think it would be fun to build up something in creative and then be able to play it in survival. Would make the creative server very unique imo :D Also this would be a good makeshift skyblock for people who really want that. Even better is that you could customize your own starting conditions. This should also include a hardcore mode for the plot where you can only go back to creative once you wipe the plot.