Completely bonkers idea!
Quite apart from the fact that the SSR clutter on radar would drive us to distraction, the lateral and height envelope of a manouvering glider is so unpredictable it would be of little use to us in atc or a TCAS equipped aircraft.
I don't know about the rest of Europe, but in my experience the UK glider fraternity generally operate to very high standards, keeping us informed well in advance of their intentions/operations, and also generally manage to stay away from similarly busy airports/airfields.