It would be a lot of work in that it's not a default feature of the theme, but how easy it is to do is ultimately relative to your level of coding knowledge. Under normal category setup, you can use the same category names under different parent categories.
If you're not looking to make the changes yourself, AppThemes does not offer customization services, however we do have a
certified partners page where you can find developers for hire. If you make contact directly with an outline of your requirements, they can provide a quote for the work. Thanks.