I'm the one who has been cutting tags for our big project at work. The problem is that its kind of a pain with a number of steps, and while I've yet to make a mistake, the chances are there. So last night I decided I ought to build a tag creator in Python.
This won't be some generic tool to release on the world. We've got some application and environment specific things going on that I can't share.
That said, I could probably do it in a way to make it generic. Basically you would create a config file for your location, a SVN externals file, and then when you would run Versionator it would create the tag with just the system version as your only parameter. And I could probably do it in a way so it would support SVN or Bizare. Maybe Mercury or Git in the distant future.