In a different thread relating to opening existing quest environments to PvP, sans monsters, I go to wondering if adding a 'Friendly Fire' mode to the 'Party' option (where you convert to raid, have convert to friendly fire) would add a different dimension to things in general.
Friendly fire would simply be the same quest as before, except you can hit people in your party. You would not be able to stand in the same spot as others, or pass through your party. You could beat the heck out of each other on purpose if you wanted to -- not really a PvP mode, but I can see people using it for that.
It seems to be this type of thing would add a huge challenge to the game ... no more wildly spamming cone of cold or fireball ... no more ranging from behind the party ... two handed fighters being give a lot more space to avoid the splash damage ... lots more communication and strategy involved ... etc.
I'm pretty sure I remember hearing that Turbine experimented with something like this along the way. While it isn't new content, it sure would make content new![]()