This is a pattern within 13 Multiple projects 
that I haven’t documented yet. It’s one of the reasons the site got a re-write: I just haven’t got round to it.
(In 2020 when I wrote the site that just got replaced I didn’t really plan for it to be updated, so ironically enough there wasn’t really a structure to allow me to add significant new content.)
You’ve identified the ‘creative agency’ pattern. They have loads of clients and each client has loads of jobs.
My partner has worked in this world and apparently each job has an agency-specific ‘job code’. I think in this case my advice would be to use that ‘job code’ as your first-level organising folder, i.e. replace my letter-number-number project code with a code that already exists and is well understood at your company.
And then under there is your JD structure. In the case of The Simpsons, I’d expect each of those structures to be essentially identical, with different assets at the leaf nodes.