How to produce a sub-page-system in WordPress

I think this is definitely possible. I can’t give you a full working example, but here are a few thoughts-

  • You could probably make services a taxonomy, then adding a service would be a matter of adding a new term to the tax.
  • you could make articles a custom post type, and associate each post to a service term to attach it to that service.
  • use the post_type_link filter to generate the URLs for each article post under the associated service. see this answer for an example.
  • you could also possibly make service sub-pages a custom post type. you may have to play with the order you register things to get the rewrite rules in the correct order of precedence, or you may need to write some rules manually.