Wing Chun isn't a style to me. Perhaps a system. More like a systematic approach to getting the core ideas across.
If I wanted to teach someone what Wing Chun was about (theory, etc), I would create such drills that are contained in the system. I would create forms to showcase Wing Chun. That way, when it was passed down, the core ideas of the system would never be lost.
Problem would be...if people confused the system/shell for the real thing...but that's for another time, perhaps.
An ounce of action is worth a ton of theory. Friedrich Engels