Each time config is updated and the plugin reloaded, all item images are re-downloaded resulting in the shop being unavailable until this is completed.

Is it possible to add caching of these images, or (preferably) an option to reload the config from console rather than reloading the entire plugin each time?

I would have no way of knowing if you change an existing image Link URL to something else.

This means if you went and did your edits and decided to change an existing image link URL to something else

Image library would never get called to update those accordingly. 

Which then in return I'd get reports about how their images aren't being updated. So yes it is possible to add that option, but it would only cause confusion and overcomplicate it for them. As a developer yourself surely you can understand my reasoning :)