Would it be possible to add an option to easily open the current repo in the default terminal, so that it's more convenient to do command line actions without having to copy the path, or open Files and then open the terminal from there?

What Reveal does for Files, but opening a terminal. You could also overload Reveal with a dropdown, similar to open, or you could combine Open with Reveal by adding fixed options at the top of the selector for Files and Terminal, and add an config option for whether clicking the button opens a terminal, files, or shows the dropdown by default.