Critical Engagements in Bozja were a fun update to FATEs that were more akin to mini raid bosses or dungeon bosses than your standard FATE is. I think this could be a fun way to implement something new and exciting into the open world in FFXIV which desparately needs reasons to revisit open world areas. In addition closing off a small area of the map means you could add higher level FATEs and content to older open world zones in order to give reasons to revisit them.