RE: 'll do the ratty rusty one as the Vorpostenboot...
Here are another ones for your inspiration. Former Yugoslavian Masor and Marjan converted by Germans as Minenshiffe - Minelayers and Minesweepers operating in the Adriatic Sea.
Masor:
Marjan
Former Yugoslavian Leader Dubrovnik - in German service - TA 32
Former Yugoslavian DD Beograd, then Italian Sibenico, and finally German TA 43