Export a mc to a swf


I want to make a online tool for designing flash banners.
I think the best way to do this is by make a swf were someone can fill in text fields and upload images into a mc. And then when the banner mc is ready export this banner mc to a new banner swf that the user can download.

Is this possible in actionscript (generate a new swf from a swf)?

If the answer is no, does someone knows a onther way to make this kind of online tool?