I was going to wait until this was better but I thought why not share my creation and get some feedback.
This program allows you to have more then 5 worlds, and have them be named. It also simplifies the theming process and provides seasonal theming support. It is currently at works for me status.
To add a new named world you will have to drop the named world into your Minecraft saves. This will probably be made simpler in the future.
Whatever you do, don't use the built in delete world command or you will lose your world. Instead, if you want to generate new Worlds, use MinecraftLauncher's unlink. This may have unintended consequences if you have not already named all your saves. This will probably be fixed when I get around to it.