It would be great if there was an option to redirect a user to a custom URL when they don't have access to a course, and maybe even switch the button text to "Learn More" when the custom URL is used. Currently, it's a bit of a cognitive disconnect because the thumbnail has a text overlay that says "You don't have access to this course" while the button still says "Open".
This would allow us to create a sales page for the course and drive traffic to it from within the group. Many LMSs currently work this way. (I know we can still do this by adding a text link to the course or module description but it's not intuitive to the user based on the disconnect mentioned above.)