An option to set opacity of active / inactive windows would be nice :-) Could be configured via "hidden options" of xfwm4 (like opacity for moving/ resizing). Of course with compositor extension only. Reproducible: Always Steps to Reproduce: 1. 2. 3.
Could be done, yes - Easy one.
I seem to remember a patch for this was floating around the mailing list, I think I still have it on my hard drive. I'll have to grep my mailbox for the source, though. If you're interested, I can attach it here.
Better use Brian implementation IMHO. It works mostly fine and does the job without bloating the window manager.
*** Bug 1125 has been marked as a duplicate of this bug. ***
Done in Xfce 4.4