Implement hook_field_access() for DS fields

I'm trying to create custom fields that are restricted per role. One could use the field_permissions module to restrict access, but this only works for core fields. So I think 2 things will be nice to have:

- Be able to set field_permissions for DS fields
- Be able to define a 'parent' field in hook_ds_fields_info() that is checked for field permissions. Use case: you already have a field 'my_field' with permissions. I want to use DS to create a 'my_altered_field' which uses 'my_field' with some alterations.

Thanks!