Hm... I am failing to see where this differs from just using the native library feature?
You can easily create or update a native Sketch icon library from external (non-Sketch) sources. E.g. in case icons are built in Illustrator, Figma, Affinity, ... . Or if the single source of truth for icons is maintained in SVG format. Or whatsoever. Potentially huge time savings in lots of use cases.