I was able to unlock the bootloader, get root access, lock it again, and use Dolby Vision (I don’t remember if I tried using DV while it was unlocked)
Unfortunately, it doesn’t seem to be possible to boot from an external device without opening the case, and there are no alternative roms to try to flash, so that’s all I ended up testing. In theory, if the bootloader is unlocked, I think both these options would be easy to accomplish for the people with the right skills.
Those are great news about the DV conversion!