Jersey pockets. I must look like some sort of reverse kangaroo or a camel when my pockets are full of clothes but who cares? Pockets don't require any setup and allow you access to your clothes while riding. I realize that you're going to stop to put on pants but I put on and take off my vest while riding all the time. Selecting clothing that compacts well makes it easier. Instead of a bulky heavy jacket, a vest and arm warmers. Instead of pants (pants? really? not tights?), knee warmers.

Wrapping clothing around the frame is a bad idea. Guess what happens when it comes loose and gets sucked into the rear wheel?

If you can't get everything into your jersey pockets, get a larger seat bag.