An interesting idea, but I am unsure if there is the demand. Anyone else want this?
Thanks for considering it, Neil. You guys are really great on listening to users. Even demanding ones like me. 
What made me think of it is the lack of Aero glass in W8. I have REALLY gotten use to glass window frames because, honestly, they are 99% useless pixels of screen real estate. Turning them to glass in W7 brought the important information to be front and center, rather than the UI overhead.
I just saw that pretty Metro weather ap (a complete waste of fullscreen real estate) and thought "the only thing junking that up are those ugly square Metro borders and buttons, I wish they could go away".
If you did give it a go, I assume it would be a "per window/ap" choice, like say, Transparency is in other Stardock products like WindowFX.
Thanks for listening.