How woud you plan a sector directory with Drupal?
Reference entity http://drupal.org/project/entityreference will let you make all the relations you need.

Also, instead of use node I will create my own entities (http://www.istos.it/blog/drupal/drupal-entities-part-1-moving-beyond-nodes) and all the connections with views.

And remember that taxonomies also are Entities, so you can create a Vocabulary that it's "Sector", and every Sector add all the fields you need.

It'll harder but it'll improve the performance.

Oskar