SharePoint Permission Management on a List

i need some help re: Permissions

This is scenario

  1. A new site on the platform. Purpose is to conduct approval on Items

  2. A Request List to which ‘Creation form’ will create Item

  3. Anyone can request Item for approval. A generic site collection wide
    SP group which contain all the members is given ‘Contribute’
    permission on this List.

  4. Once Item is created; a workflow in triggered( through Nintex 2013
    which is the workflow engine )

  5. The workflow consists of getting approvals from various actors.
    Conditionally; the workflow may special approval. This involves
    filling up a sister form and creating an item in the Special
    Approval List.

  6. Want to restrict permission on the Request Item such that only the
    current actor is able to edit Item details. initially; we have given
    ‘Contribute’ to all members who will be using the site.

Methods considered

  1. Change permission once the workflow starts using ‘Set Item Permissions’ action such that the person who Requests cannot edit
    Problem—> Information on the net points out that setting Item level permissions can get messy very quickly and not a recommended soln for performance consideration

  2. Run the workflow steps as ‘Workflow Owner’. This solution involves giving the group with all the members ‘Add only’ permission so that they can create a request but do no editing on it. Workflow actions which involves modifying the List item will be executed as Author who publishes the workflow
    Problem—> This could potentially work. We have noticed that some Workflow tasks are created twice when it comes inside an ‘Action set’ that is set to execute as Author. Another thing is that we want to give the ability to Save drafts; so ‘Add only’ permission does not meet this