How about introducing a new frame parameter: topmost . 
If this parameter is true, the frame is shown as a TOPMOST window.
 
It will be quite useful. e.g.,
 
1. During ediff, the small ediff frame can be set as TOPMOST frame. So it will not be hiden when we need to edit the comparing file termporarily.
 
2. Sometimes we may like to pop up a small information frame (e.g., *help*, sometimes we may prefer to pop up a new frame instead of spltting the current frame/window), and at the same time, we can edit file in another frame. The information frame is set as TOPMOST, so it will not be coverred by the edit frame. And so we can easily refer to the information when we are editing our file. It will be very nice.