ActionScript 2.0 :: [mc] Replacing A Movieclip Without Changing It's Children / Depth / Tweens

I would like to be able to draw a simple box as a background/placeholder, dress it up with buttons and movie clips at design time, and at runtime call a function to replace the simple box with the new design. How would I go about doing this? I have a graphic design that is too complicated to make with flash. So i made a piece of actionscript that can restyle any existing movieclip. This piece of code works. It basically gets the coordinates of the specified mc, creates a new one in it's place and deletes the original. Unfortunately this also removes any nested movieclips and buttons and breaks animation tweens of this mc. So if the original mc would have a button on it and animates from left to right, the new one doesn't.

mc.clear(); looked very promising, but it only clears stuff you put on it at runtime while I need to clear the stuff from design-time. (= the simple box drawing object)
Creating a movieclip with the same name, at the same depth doesn't seem to work. oldbox.parent.createEmptyMovieClip(oldbox._name, oldbox.getDepth()); The old movieclip keeps existing and neither of them animates.So I'm searching for a way to replace a movieclip or clear it's content at runtime. Or am I thinking in the wrong direction and are there other ways to restyle a movie clip?