let user create content as another user
Using node hooks to set the user will work, but what you are suggesting is really what is normally called "workflow" in content management systems.

There are a few ways to do workflow in Drupal, but the most common for Drupal 7 is probably using the Workbench suite of modules.  In particular, Workbench Moderation would be the most beneficial module for your situation.

You would set up a few different roles (writer, editor, proofreader, etc) for your users.  You would then set up various workflow states (Draft, Pending, and Published are a good start).  Then, you define which roles can push nodes through which states of the workflow.  For example, you may say that only writes can push from Draft to Pending, and proofreaders can only push from Pending to Published.

In the long run, this will give you the most flexibility as your current situation evolves and changes.