The way how to remove policies from an object should be explained in more detail.

Here is how I understood it:

• Get the object and identify the policy id you like to remove.
• Fetch the policies collection of the object.
• Walk through the feed and find the policy object where cmis:objectId == policy id to remove.
• Get the self URL of this policy object.
• Perform a DELETE on this URL.

That looks pretty expensive to me.