I think I want to use site nav to populate these tabs... so that I can add and edit them via the interface and that they are sensitive to the page status (eg not showing an annon user a page that is in under-construction.

Along with account settings can have user site preferences (eg size of fonts). Annon access OK.

If user is not logged in this can be the ONLY active tab... to cntrl font sizes, etc. but there could also be a login form (or at least a link to login page). Could think about it because it would be nice to have messages too.

It sure does!