I understand what you are trying to do, but you cannot do that with PlantUML today. This will be probably released in future version.
The current version of "hide" key word does only apply of some part of the class (member, stereotypes...) but not on the whole class itself. Example:
@startuml
class Foo1 {
dummy1
}
class Foo2 {
dummy2
}
hide class members
@enduml