YUP: I think this would be super handy!
You can do this currently, if you don’t mind running things on the terminal and are using either PhotoStructure for Servers:
https://photostructure.com/server/tools/#manually-importing-files-and-directories
But making this “just work” would be much nicer. I’d thought of adding a “quick sync” option that visits the last N grandparent folders that new assets have been found in.
This would also handle it, I think: