There is a very simple solution for this!

create a variable that does not get destroyed(global kinda). If your using the CS3 interface just place it in the actionscript part of the stage. If your using the sdk to compile just make it a private var in your class.
After setting it for the first time add it to the myemptyMC object.

when you want to make that variable something else just reference it(set it) to another object.

Example


Code:
var child:Object=mySwfLoader;
myEmptyMC.addChild(child);

//this changes it to a new thing because I'm setting child which is already added to the MovieClip to something new
child=new Object();
Hope this helped !

If not just ask about what you don't understand.