Can you share why you are running a validation of the logged in user?
You could automatically capture their name and have them check or toggle a field. This would use the User Profile Service to fill in their name and then they would mark some field value as needed. Also while this is complex, you could potentially only allow them to update the area they have edit access to. So the workflow would move the process along and after each person, it would modify their permission so that they no longer can edit it once they have completed. You would then need to make each section editable only based on a status. This is a lot of work, but doable. Just need to understand what you need from a business perspective first.