The requirements for my project have changed some, so my original question is no longer necessarily relevant to me, but for any future users looking to control their Canon DSLR over USB from an Arduino, this website has some pretty cool info:
https://www.circuitsathome.com/canon-eos-cameras-principles-of-interfacing-and-library-description/
https://www.circuitsathome.com/canon-eos-cameras-principles-of-interfacing-and-library-description/