Automatically Select Topic Category Based on Post Category?

I have a custom post type of policies with a hierarchical custom taxonomy policy_categories on two levels (parent/child). There are about 45 child categories.

I’ve set WP Discourse up to publish to a Discourse category of policies, but rather than create a huge set of subcategories (having read around this forum) it seems better to create the subcategories as tags.

I’ll have various Wordpress users publishing policies with different experience levels (if it were only me doing this I’d just tag them every time). So to save on an extra step and probably a chunk of support hassle, ideally there’d be a filter to get WP Discourse to take the Wordpress Categories and add the matching Discourse Tags.

I’d be happy to make sure the categories and tags match IDs/slugs etc. as I’ll be holding any updates of these as admin.

Thank you for your help on this.