Andra,
That type of powerful expressiveness is certainly doable in Wikidata. To blatantly create properties on a whim by pseudo proxy of using Wikidata items to do the heavy lifting. But that idea is against most of what I have seen in Wikidata documentation, policy, and community best practices say to do.
The right way forward is to patiently wait for the new property to exist, and then we can continue. Thank you for drafting the property proposal by the way. I'll wait for it for review.
Here's some examples where we have subclasses under these :
https://www.wikidata.org/wiki/Q4026292 Action should also ideally have all of Schema.org's subclasses of Action that we have like http://schema.org/TravelAction
https://www.wikidata.org/wiki/Q11410 Game should also ideally have the subclass of Videogame http://schema.org/VideoGame
Here's an example of flipping it around and saying that Schema.org can be used as an 'external parent class' https://www.wikidata.org/wiki/Q7889 Videogame should also ideally have a proeprty on it for 'external parent class' or something similar with the value of http://schema.org/Game
Our full heirarchy is here for your perusal : http://schema.org/docs/full.html
Thad +ThadGuidry https://www.google.com/+ThadGuidry