Cleanest way to dynamically target library child MC?


I got a simple question that confuses me alittle, cause I want to code the best way.

So, I’m using a document class file to manage my animation and I took the habit to work with linked class names for my library MC.

In my code I got something like :

public var BoxMC:_Box = new _Box();

and then I use the common addChild and other functions to work with it.

Anyway, my website template is composed by a lot of separate MC and I thought it would be easier to wrap them all in a single MC (easier for global centering on screen and so on)
I still can access the children of this new born MC with codes like :


But is it a good usage of AS3 ?
What should I do if it’s bad to create simply a global container that hold my separates MC and still can target all the children easily ?

Thank you !