Apple - Folder-based photo management software for local use

You basically have written the summary requirements for Photo Mechanic.

It's a folder based, workflow tool that is cross platform and highly optimized for managing images. Whatever changes it makes are stored in metadata in the images so you can edit them elsewhere as you please and it won't break import/export like library based workflows cannot do.

Given Lyn is close to your needs, consider combining it with other applications. Such as:

• HoudahGeo offers a graphical interface for tagging and searching photos by location.
• exiftool is a command line alternative from which you could craft any scripts or services you need.