I was about to post a topic about collision detection but I searched for it first to avoid duplicate topics. Ha, you posted this topic on the same day I was about too.
I think Crowfall can approach collision detection by making a hybrid collision detection system. For example, collision detection should be activated by combat and enemies. This avoids problems like tera online had at launch. When I first got tera and logged in, I was stuck and surrounded by other players. Crowfall should allow players on the same team, faction, or guild to go through each other if their not in combat. For example, combat should activate collision detection between friendly players. Areas of large combat and wars should automatically activate collision detection. A player should not be able to go through another player if their in combat. A player should not be able to go through an enemy player or enemy Ai as well.