Taxonomy term creation permissions

Anybody got any good ideas for how to limit editing/creation permissions for specific taxonomy vocabularies? Here's the deal, I use taxonomy breadcrumbs, taxonomy defaults, and other modules to manage certain navigation aspects of my site. Therefore, it's really important that office staff managing content on the site not alter/delete certain vocabularies and their associated terms. As a result, I have barred them from administering taxonomy though access controls.

There are a few taxonomies, however, where I would like office users to be able to add/modify terms. It would be great if I could drill down taxonomy.module permissions to the vocabulary level.

My work around for this is to use the tagnode module. I've created a custom CCK node type that's just used to create tagnodes and taxonomy terms for a specific vocabulary. This works - but I'm worried about tagnode depreciating after Drupal 4.7.

Any thoughts?

Cheers,
sean