Here are my thoughts on several mega events.  Some may already exist in one way or another.  Either way I don't think there are enough of these currently in the game and would be nice to see more of these events added either via expansion or dlc.

Existing Mega Events

Dread Lord Event

• Similar to Galactic Civilizations III The Dread Lords should get a full planet of Industrial Sector buildings.
• Similar to Galactic Civilizations III The Dread Lords should start with higher level weapon/soldering techs to make them a stronger force.
• Dread Lords should be more aggressive in taking over systems.

Anomalies Event

• Should be able to happen multiple times throughout the game.

Future Ideas

Distablilize Galactic Empire (Don't know if feasible but think it would be awesome)

• Trigger if leading players control is over 50% of Galaxy
• Trigger if leading players moral drops below 70%
• Action Any original homeworld's of any starting faction for minor or major race break away from the larger empire as their original factions.
• Action Those new factions have equal to techs of the larger leaders faction and control all existing ships in orbit and get free transport ship
• Action Those new factions also get small fleet of most powerful ships available at 50% hit points.
• Action Those new factions also get +3 planet quality for new buildings.

Planet Transformation

• Trigger if player is falling behind but, not at war
• Trigger if moral is over 80%
• Action All dead planets with-in x tiles of homeworld are now habitable ranging from class 4-10 or...
• Secondary action if not regular habitable than extreme planet class 8-18.

Extreme Action

• Trigger top 10% factions are more powerful than next 20% combined.
• Action all remaining habitable planets are now extreme planets.
• Bottom 25% Get Extreme planet technologies.

Separtists Movements (multiple events, with multiple new factions [possible dlc])

• Trigger on any faction moral less than 70%
• Faction split via civil war to X faction  This will contain all planets with-in x tiles of the new homeworld.  That way it's not culture flipped right away.
• Trigger 2 on any faction moral above 95%
• Faction split via civil war as extremists want to rule their way and want to take advantage of the weak.  Same critea as above.

I think some of this would be nice. What do you think?