Blanket CCK Field Permissions for Specific Content Type?
"Editing a field" can mean a lot of things because a field has many properties for input ('widget'), storage and output ('formatter'). That's why I was trying to figure out what you're after.

If you can write PHP, anything is possible, but I think that introducing a way for content creators to edit (a limited set of) field settings, would require a lot of custom code. However I assume that you're looking for a solution that requires no (or a little) custom coding. In order to achieve that, you may need to choose an alternative solution, like a custom compound field, CCK Multigroup or Webform. However I cannot advice you about that because I don't know which problem you're trying to solve.

On a more theoretical level, I think you have to be careful not to get content and configuration mixed up. Drupal stores both configuration (like field settings) and content (the information in a node) in the database. What you're asking sounds as if editing the field settings would in fact become another way to enter information. That may not be a problem now, but it can become a problem later because other modules are not prepared to access field settings as if they are part of the content.