How to manage Item attribute Update at Inventory org

Business requirement. Create 3 distinct roles to manage the Items across Inventory Orgs.

1. View Only : Create a view only role to view the items assigned to the inventory Org.
2. Item Create : Create an item role which enables the data stewards to create as well as edit the item attributes.
3. Item Update : Create an item update role to enable the users to update the item's operational attributes e.g., processing days, planning type flag at inventory org.

We are able to meet the requirements of listed in point A&B, but unable to achieve requirement C. We are unable to create a role which allows the users to edit the item attributes without creating the item ( as listed in privilege 'Manage Item')