Many gadgets today work or are intended to work only in some specific skins. It can be because the gadget "fixs" some issue in a specific skin, or because it is legacy gadget working only in some specific skins. (As you can see in [[:en:Special:Preferences#mw-prefsection-gadgets]] by searching "monobook" or "vector" there are already many scripts that work only in some skins).
Currently it is possible to mention specific rights needed for the user in gadgets-defintion in the format of:
I would like to request the same for skin - to declare for a gadget that works only in one or more skins.
This can be achieved easily by adding a small if in Gadget::isAllowed + another case in Gadget::newFromDefinition.