What if one hovers over an app in the taskbar, all the open windows is made transparent, and the hovered app gets a flashing (or non-flashing, your choice) halo? (Halo or shadow, but shadow is a more colour-independent description)
How it could be implemented is by on making the windows transparent, all the open windows could be converted to OpenGL-textures (and then be made transparent), and so not hogging the CPU-resources.
If there is a positive outcome, I'll post it to the kde developers. I'm not even going to dare doing it myself (no C++ programmer, just a fresh Delphi/Windows convert), but this feature is one I really like to see make it's way to KDE4. This is very kompose-ish, but would greatly improve the ui.
Please leave your thoughts.