This would be low/high sec only.
Gates are randomly attacked by NPC pirates and are taken offline until players clear the gates. Rewards when the gate is clear (mission objective?).
It is mainly a good clean sandbox style PvE activity that could get pretty messy in low sec
EDIT1: The NPCs would not stop at one gate and would never release a gate unless the players retake the gate. Eventually if ignored inhibiting travel and isolating systems.
EDIT2: No loot, only the mission reward for clearing the gate, to avoid farming.