I
believe you can get away with just swapping out the Screen Element <Pieces>.
Don't quote me 100% on that. I've never done that before, but there isn't any "defining" elements in both of them windows.
As far as EQ cares, you can completely remove all the Piece elements from both windows and be fine ( unlike some other windows ).
Oh, and make sure you get the Size and Location information from the two Screen elements switched, too.