If what we actualy need is a BTS entry for the system in general (e.g., gnu), Debian GNU/Hurd isn't the GNU system, it is a variant. this should be requested to the BTS admins (by using the BTS, of course). Using the "general" virtual package. Why not just create a category for the ports instead, call them BSD, GNU/Hurd and GNU/Linux (or go by kernel) where one can assign bugs accordingly? Seems far more flexible in the long run.