Absolutely can power camera and send USB API commands. Will work for months. See below.
Consider Power over Ethernet for the Raspberry Pi and then USB power to THETA with control from USB API.
gphoto2 works
But not the entire command set in my tests. You may get better results.
I know a developer that is going to release more code for the USB API for the THETA this month. Things may get easier. I haven’t used the code yet.