Changed subfolder to [month]-[day]_[jobname] and checked "Ask each time for jobname". That works perfectly! Now I only need to group the files to download into several batches if I have more than one event on the card. That's easy!
My workflow is yet again smooth and perfect. Simple and perfect solution.
But now what to do with all my folders just named [MM-DD] without jobnames... I still want a rename function. Not so important anymore, but on my wishlist for future versions.