This isn’t for creating aliases, it’s defining mappings of a command to the plugin implementing it. If, for example, say you have two plugins with a /repair command.
aliases {
repair="nucleus"
}
This tells Sponge that the command /repair should be controlled by Nucleus (nucleus being the plugin id).
In your case, you’re looking to set up an alias for a command; not redirect it to a plugin. There are a couple of plugins that can handle aliases, one of which is my plugin CmdControl. There’s plenty of resources to help get you started, and I think this is what you’re looking for and then some.
As a final note, it’s generally better to create a new thread than bump really old ones - this was posted well over 2 years ago!