@ David,
There was that GUIStudio that 'Andromeda' did for DBPro a few years back. That showed some promise.
GUI that worked on top of a 3d camera, with ability to change / alter fore and back colours and textures, scroll within panels and then pretty much what wildbill and VanB say. Clocks and dials, fluid cylinders (health etc), compasses, sun and moondials... the list is really endless and I'm sure you have all the basics....
If it were founded on a solid .dll plugin for DBPro with plenty of media of yours, I'd go for it...
p.s. knowing your graphics, sprites etc, ever thought of creating a plugin .dll to help with isometric 2d?
[edit]
Just spotted this thread:-
http://forum.thegamecreators.com/?m=forum_view&t=176945&b=1
Would be great if you could have a v flexible plugin for DBPro with your media knocking out stuff like you and 'The Slayer' are demoing on that link....
a long time dabbler with DBC and DBPro with no actual talent but lots of enthusiasm...