I am a huge fan of the new symbol override feature and I use it extensively in one of my projects.
But one thing that could improve usability massively would be the option to toggle certain elements on and off via display property: none.

For example, you could create a breadcrumb navigation with the full layout and depending on the page and therefore nav hierarchy toggle unnecessary elements display property to "none".
And then you are left with just the right amount of breadcrumb elements.