Handle permission based on both person and role? I am using workflow module for a publishing website. 

There are many people who have the role reviewer....The comapny want to enable that when you change state from 'in moderation' to 'in-review', we can assign the content to a reviewer through an autocomplete field. NOT ALL reviewers.

Workflow content permissions does a great job, for making it role based. So the author is no longer allowed to edit the article when it is 'in-review' state. Now I don't want to allow all reviewers to edit it 'in-review', only the one that has been selected.

Is there a module for this? If not, how should I be going about this.

P.S. -: I am barely a few weeks into Drupal, so go easy :-)
I suggest first to use the Rules module to fire an action on your workflow transition : from 'in moderation' to 'in-review'

Second try to use the Node access user reference module or the Nodeaccess module to use an API method inside your a custom PHP code or as a rule's action to grant the referenced user