Don't know if this will help or not, but I did this for a clubs website. I get 3 levels of access without editing abilities (like a second registered category) for author level.
This is a core file modification, but is easy to make.
In the file: includes/
gacl.class.php. I made these changes under where it says actions at about line 178 or so The original line is remarked out with the new line above it:
In the line $this->_mos_add_acl( 'action', 'add', 'users', 'author', 'content', 'all' ); I removed the word author. There are two places in this section to do this. I copied and pasted the action section below from my gacl.class.php file with the mods made and commented. Use if you like, but note this is only the top sections of actions where the edits were made.
// actions
//Modifications added to remove author level actions. Original line is marked out. 12-17-07
// This prevents changes from being allowed by authors enabling you to use the author registration level
// for club members.
$this->_mos_add_acl( 'action', 'add', 'users', 'content', 'all' );
//$this->_mos_add_acl( 'action', 'add', 'users', 'author', 'content', 'all' );
$this->_mos_add_acl( 'action', 'add', 'users', 'editor', 'content', 'all' );
$this->_mos_add_acl( 'action', 'add', 'users', 'publisher', 'content', 'all' );
$this->_mos_add_acl( 'action', 'edit', 'users', 'content', 'own' );
//$this->_mos_add_acl( 'action', 'edit', 'users', 'author', 'content', 'own' );
$this->_mos_add_acl( 'action', 'edit', 'users', 'editor', 'content', 'all' );
$this->_mos_add_acl( 'action', 'edit', 'users', 'publisher', 'content', 'all' );
$this->_mos_add_acl( 'action', 'publish', 'users', 'publisher', 'content', 'all' );
~~~~~~ rest of section actions here ~~~~~~~~~~
Club members are set to "Author" level and Content set to "Special" is only viewable to them.
The end result is club members are author permission level but they can't perform any "author" level actions.
Regular people can still register on the site, and also buy things from the store without accessing anything that is club members only. This solves the problem of giving "more private" permissions to club members without the ability to actually do any author level editing, having a login module visible, and still letting non club people register to purchase items from the store.
Guests and registered members will not see anything that only club members are supposed to see. Club members once logged in will have additional menu items, sections, etc. available to them, that registered users don't .
The mods I made were based on the information I found here:
http://demo.joomlaworks.gr/content/view/23/32/
The link provides information on how to make other permission "adjustments" and is worth a read and was the inspiration for the above mod.