When I tried extremeUI I found that the chatwindow etc was visible while loading a new area. I didn't like the UI very much, but I like that feature a lot! Do any fix exist that allows this without using the extreme UI?
FetishUI has something similar that lets you see everything while zoning/loading.
It shouldn't be too hard to take the zoning file out and add it in from whichever UI you like... some might have it as a standalone to make things easier, not sure.