Greetings, the administrator of *Skinning here, and I've got some bad news for you. Unfortunately, your beautiful idea for a theme wouldn't be possible with themes because the Windows API and GUI doesn't allow for transparency without an external program. You need to run a program like Windowblinds to have transparency, but even then you have limitations as to how much can be transparent. I don't recall how much of a window can be glass or frosted glass, but I can tell you that when you go into the primary window (where text is and et cetra) CPU processes really start to slow down and chug, therefore Microsoft recommends you keep it to the sides of windows and the tops and bottoms, and the start menu so the computer doesn't have that much to render with your graphics card. I think it makes sense if you think about it.
just search it on deviantart.com and its only for Win7 I think
The only way to get that is coding the app with the right code, (look at vistabootpro). (In vista)
Great idea though!