Hello Super Joomlers!
Breaking news! I decided to share a plugin used internally in my company to the Joomla! community for free on Github.
It allows you to define access level not just for groups as Joomla! actually do, but also for individual users and even both.
Its called COOPACL because it cooperates with Joomla! core ACL. It's a system plugin. You just install one plugin and voilà!
You will automatically have new functionnality when you go in your Joomla! backend in the access level menu.
Now, when you create a new access level you can choose, a group (eg: Registered), a user (eg: Example User) or both.
In the access level list view you will see the selection accordingly.
Thanks for your time.