I am in a bit over my head with this one, so I'm hoping someone can point me in the right direction.
I am working on a project that involves a complete overhaul of a site that currently has over 22,000 posts/pages etc. On the existing site, they have three (relevant) taxonomies that each post can be assigned to: audiences, tags, and categories.
Their tags are out of control (over 3500 unique tags, most of them with less than five associated posts), so we opted to just eliminate tags altogether, as they are not helpful for their situation. There are about 30 categories, and a post can belong to as many or as few as desired. There are five 'audiences,' and currently, a post can belong to any number of audiences. The 'audiences' taxonomy is only used as a holding group for other functions, and is not used on the front-end of the site.
The decision was made to redo how posts are grouped together, and place heavier emphasis on logical grouping. Even though the client was not really using 'audiences' on the front-end of the site, we have decided to use it as a base for grouping all additional content together. This would form the first tier of our navigation, with sub-navigation being all the associated categories below that.
So, my question: assuming I make no changes to the taxonomy structure, given a specific 'audience' term, is there any way for me to list out all associated categories?
To put it another way, lets say that I am on the "Consumer" audience-taxonomy archive page and want to list out every category-term associated with any post that is tagged with the "Consumer" audience term (mind you, not list the posts, just list the category terms).
Alternatively, my thought was to bring all the "audience" taxonomy terms over to the "category" taxonomy, and manually assign categories to one parent (the old audience terms). Would it then be possible to is it force a user to only select ONE of these parent categories (old 'audience' taxonomy terms) and then display the child terms and allow them to select any number of child terms for that parent?
I know this is a little convoluted, so I apologize if this is hard to follow.