ActionScript 3.0 :: How To Replace Symbols At Runtime

My game will have plenty enemies, and most of them belong to a "group" or "kind" of enemy, which will act pretty much alike, with the difference of a "skin". I've made a long movie clip with a generic soldier with all the animation available trough labels and ActionScript (e.g.: for setting the walk animation in the enemy, I just do [enemy].gotoAndPlay("walk") and starts a looping animation, same thing for stand, fire, dying, etc.

What I want, is to create different monsters at runtime, just by replacing the symbols within the MC attached to the class, so a red soldier and a blue soldier will have the same animations, and both can be displayed on screen at the same time. This will be done at the constructor of the class, exporting the MC for Action Script as Monster and creating a class MonsterRed which extends Monster, and in the constructor method I replace every part with the ones I want.

If I didn't do this in runtime, I'd had to create a movieclip for each monster, and if I change some animation I'd had to replicate the movement for every monster of the same type. I could do this by making every part such as leg or arm of the monster as a movieclip with different styles in each frame, and switching between the different "skins" using [enemy].[part].gotoAndStop(x). But this is a very dirty workaround.

One clear example would be the same monster carrying a different weapon, the only symbol to replace here would be the gun symbol (and changing the behavior of this new monster, of course). How can I swap the symbols attached to a Class at runtime? So different classes inheriting a MovieClip exported for AS3 could have the same animation with different symbols.