I don't like the hardcoded version neither... but there is no file where to get this information. As you said, i will need to create another file but I don't see how to do it.
I suppose you're talking about a file containing an hardcoded majore version which will be added into the Makefile of each package ?

Futhermore, others problems here:
* The files downloaded are not exactly the same that the files which are builded (some missing and rudder-doc.html become index.html)
* I'm downloading these files into the directory 'rudder-doc' but actually, these files are installed into the folder 'html' and dh_install is not able to rename file or folder.