score:4
I wanted to report back that I attended the visa processing centre last week to submit my application. As "proof of legal status" I brought my MeldebestΓ€tigung fΓΌr die Anmeldung to show I live here and my latest Entgeltnachweis to show that I'm employed here. The visa staff had no idea what these were and, after I explained things, they seemed mildly annoyed that I had included such irrelevant documents in the application. They returned them to me before accepting the application for processing. All they kept was the signed application form (including my photo), my passport (and a photocopy thereof), and my hotel and flight bookings.
I picked up my visa earlier today without any problems.
So for me, no "proof of legal status" was required. YMMV.