Add-on Display Members who have permission to see Forum

I posted the following suggestion in the "Implementing permissions across multiple user groups" thread, but am adding it here because the functional does not currently exist and I would be willing to support its development

I'd like to be able to display the forum members who have access to each private sub-forum I've created. Is there a way to do this, perhaps through a user-facing widget? Some users are reluctant to post in a forum as they aren't sure who is or is-not seeing their post, and I'd like to clear-up this confusion. Thanks in advance for any suggestions.