When rendering animations, you can select "Sequence Type" as Macromedia Flash. There are also settings for the format. The easiest way to convert clothes in this fashion, a skirt to loin cloth or long-sleeve to short-sleeve shirt for instance, would be to use a transparency map to "virtually" cut away areas of the clothes. Transparency maps are just gray-scale images where black (0,0,0) represents total transparency and white (255,255,255) represents total opaqueness, grays varying inbetween. If you take the clothes color texture map, convert it to gray-scale, then make the textured areas white and everything else black, you can black out white areas to remove cloth from the clothes. This is then applied to the transparency channel of the clothes material.