I don't believe the technology has reached the point where selective interior portions of a window can be transparent/translucent & the remainder opaque. Since borders can be trans, and entire windows can be, I suspect it's only a matter of time, however.

I find using a lot of transparency to be visually awkward, personally - has the effect of "cluttering" the screen with stuff unrelated to your current activity. My preference would be a standard opaque active window with all inactive windows going semi-trans or gray-scale. But to each his own.

Seems like I've heard or read of a program that will semi-trans inactive windows, but I don't recall the name. At the moment, there is not a way to designate an alternative image or color for most of the inactive 3D elements, the exceptions being the Titlebar and remaining borders and the Menubar.