I'm not sure I'm following what you're trying to do but why don't you download the video then import it into Logic as a movie. After that you can put as many tracks on as you want then bounce the movie with your added parts. It's pretty easy.
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Mac OS X 10.12.3
Logic ProX 10.3.1
Audient iD22 Interface
Focusrite Pro40 FireWire Interface
Digidesign Eleven Rack