As it stands the threat posed by some of the mega events, Dread Lords and Peacekeepers in particular, can be minimal on larger maps. By the time they appear the player is usually advanced enough to eliminate any threat they could have posed.
Could the threat level of these events be an option on a slider with minimal, normal, high and suicidal? On normal the threat would be as designed today. On high and suicidal the Dread Lords and Peacekeepers appear with significantly more advanced levels of weaponry and ships as well as higher production levels and more logistics to build bigger fleets. The mega event with the artifact could also be tweaked to provide significantly more production to the race that gets it on higher levels, making neutralization quickly that much more imperative.
On a related note, would it be possible to make them player factions? Playing the dread lords in sandbox or even in a DLC scenario would be interesting.