Well, to hopefully inspire someone of authority, I have actually modded The Unarchiver to have a HUD display. This shows that it really is simple enough for an Interface Builder to do (with the new dev tools). Here are some preview screens and a download link to the nib files i modified. The HUD needs a custom status bar, but hopefully this will help speed up and motivate the HUD interface into an Unarchiver release. I like it a lot and I think others will too. Also, The Unarchier rocks! thank you for the development!
Example One: http://www.randomstorage.com/mods/unarchiver/UnarchiverHUDExample_1.png
Example Two: http://www.randomstorage.com/mods/unarchiver/UnarchiverHUDExample_2.png
Unarchiver HUD NIBs: http://www.randomstorage.com/mods/unarchiver/UnarchiverHUD_NIB_Resources.zip