I have an idea for a plugin that will let players create portals to other worlds besides the nether. You'll be able to configure which blocks creates a portal to which world. For example, a portal made out of diamonds could lead to 1 world while a portal made out of gold blocks could lead to another world. These portals will work the same as nether portals but are made out of different materials than obsidian and will lead to different worlds. This would be very cool for a survival server.