Allow all categories by default

I need to subscribe members, but NOT restrict content. I am using subscription for something else, and can easily set that up via the pmpro_after_change_membership_level hook, so that’s fine.

However new categories are very regularly added on this site, and there will be several membership levels, so having to go through them all and update category access each time a new cat is created would be a real pain.

Is there a way to do this via a hook or filter? Or, even better, is there any possibility of adding an ‘All categories’ checkbox?

http://wordpress.org/extend/plugins/paid-memberships-pro/