But your problem is about generating one. You need to generate it whenever you link to pages of your addon.
Parsing does not happen in vB. That happens in .htaccess. You need an .htaccess entry that changes
Code:
/marktplatz/9-da-vinci-code
back to
Code:
/marketplace.php?do=article&id=9
Look at vB4's existing .htaccess file to get inspiration.
Edit: OK, rereading your post, you already know that and are explicitly asking for that

But don't forget: the htaccess alone will not suffice - you also need to properly generate the URLs in vB. I am, however, not sure what a "german rewrite" exactly means...
Anyway, rewriting as you wish seems problematic, since you have two parameters in your standard URL, but only one in the friendly one.