The real question is, what are you looking for, an Event or a Challenge, either combat or non-combat, by a team/squad or individual?
KOTH and Combat Challenge were successful for many years when the player count was way higher. They were just dogfighting for the fighter guys.
Snapshot, Fortress Europe, and Sunday European Campaign were popular due to the attack and defend design. They had the fighters, JABOs, and bombers for broader appeal.
Those 5 events are most likely dead in the water with current numbers. Resurrection isn't likely unless numbers improve dramatically.
The ideal new event should be unique and different from FSO and Scenario. Something that gets the player's attention immediately. That can create buzz and excitement. AND deliver on expectation.