Yes this must be annoying, and your problem comes from soemthing very simple. The open command must recoed a filename when creating an action.
It is a shame cause actions record much detail about the settings used in a raw conversion.
But I think I have found a solution. When choosing batch there is a checkbox for Overide Action open command. Make sure that checkbox is checked and I believe that si what I used ion the past to get the result you need. Let me know how things turn out have to work again this weekend put out some fires.