Would be nice to have a layer feature that you can wear more than one shirts like a t-shirt for example, but you can design a external jacket or scarf and you can always wear jackets, scarves, or even a tie with your different colored shirts.

It'll bring more variety of unique and innovative piece of clothing.

Would be cool

2d layered clothing would be nice

yeah, thats actually a pretty cool idea.
and also different categories for each type of 2d layered clothing
like shirts, hoodies, neck accesories, etc.