GUI Dialog Mods don't require any particular object type - they're just
hints about what's going on with the GUI. Limiting them to meshes
actually breaks the Note Popup modifier, which attaches a GUI Dialog
modifier to an empty.
This means you can't add VisRegions to your GUI pages. You also can't
make an empty object be a panic link region. Those kinds of things just
don't make sense.
Our calculations try to fill the entire screen with the GUI objects. So,
really, what we want the GUI Camera scaling to do is allow the artist to
make the GUI smaller onscreen by pushing the camera away. This is a
*less than* 100% scaling.
This adds just enough plumbing to be able to export GUI popup notes
using the standard xDialogToggle.py. There are still a number of TODOs
and FIXMEs in the basic stuff, but the design is mostly solid. The idea
is that you'll create a GUI page for any objects that need to appear in
a GUI. The GUI does not require an explicit GUI camera, however. For
now, an automatic GUI camera will be made facing the largest object's -Z
axis.