Entity based field permissions

There is a possibility that this might be viewed as duplicate of #1221186: Bundle based Field permissions, however I believe it differs in that I am requesting granularity of entity rather than bundle.

Use Case

I am using the term_access module to limit access to content for, let's call it, Role2. The term_access module allows limiting content access by using the same field within the node and user entity. If the user is tagged with a term that matches the node then they have certain configurable access to the node.

However, I personally don't want to allow Role2 to edit the taxonomy term reference field that is in their profile, I only want to give that permission to the administrator role. Hence, I would need different field level permissions on two entity types.

Now that is certainly not the only use-case here. As I am sure that some would like to re-use fields across entities with some differing permission settings for other reasons. Additionally, there could be a flag per field that allows turning this setting on/off and that would minimize issues with upgrade path and/or management.