As of now, Crowd does not provide the ability to use local group membership for CONNECTOR directory type. Due to your query, we proceed to create a feature request regarding this issue here:
We highly recommend you to add yourself as a watcher so that you would be updated, vote on it to increase its popularity and please feel free to address your concern directly into it. As I believe this would be a good addition for Confluence I have personally add my vote into it to raise the popularity of the issue.
For more information about how Atlassian implement New Features, please see the Implementation of New Features Policy.
Furthermore, if this is a more urgent matter, we can refer the case to one of our Experts, that provide professional services and could possibly create a tailored solution to implement the functionality.
Please let us know if there is anything else we can do. Thank you for your understanding.