Currently you can only take llDamage in damage enabled parcels. Obviously this is ideal to keep players who do not want to take damage or die safe, but could you add an opt in option to choose to allow damage to affect your avatar at all times anywhere while enabled?
This would mean that players could "turn on PVP" and engage in damage systems anywhere in SL, on any parcel, opening a huge amount of potential for combat focused communities to expand.
Those that leave this "PVP Mode" disabled would not be affected by this change at all, and would remain safe unless they chose to toggle it on and jump into the action.
Maybe avatars with PVP enabled would display it above their name and group tag, for example:
(PVP)
ECHELON
Grave
Maybe a PVP enabled avatar dot on the minimap would have a small additional red ring around the dot.