Thanks!
As for increasing action ratings, I've just completely forgotten to write about advancement lol. In short, on the charsheet there are 5 dots near an attribute name -- each time you gain XP you can put it either into one of the attribute XP trackers or into playbook XP. When an attribute tracker fills up, you can increase one of the action ratings by 1.
I don't plan to add more playbooks, at least at this point and, honestly, I don't really know what kind of playbook is there to add -- pretty much every fantasy archetype is already covered.