Readonly Permission to Requester after form submitted

Hi,

I am running through a scenario where I am required to give ReadOnly Permission to Requester when request is submitted.

Note:

1. I am using state machine.
2. The workflow has 4 levels of approvals, at each stage I am setting the Status Column as following, “Approved By Supervisor”, “Approved by Superintendent”, “Approved by Dept. Manager” or “Approved by HR”.
3. As the workflow runs with Initiator permission, I am unable to  set to readonly. If I set readonly permission for the item level then the workflow is failed as it is unable to update the list using status column.
4. I am unable to use impersonation using “Action Set” as Action Set doesn’t provide option run as Publisher account.

Please suggest me what is the best possible solution for such scenarios.

Regards.

Ashraf