[Suicide Junkie]

I wonder if it would be worthwhile to consider a multi-level game:
- at one level, we have the standard player races doing their thing.
- in the background, unseen by most players until the advent of advanced sensors, two or three non-expanding monster races battle it out.
- and at the bottom, we have a universe-eater with SM technology.

The universe-eater should probably eat all the systems at the edge of the map, then work slowly inwards, cloaking all planets, asteroid belts and stars with colonies and cloaking bases.

The winner of the game would be the player(s) who control the Last starsystem in the core of the galaxy.
The middle-monster races would attack this core system as their primary goal, preventing any one player from fortifying it until the Last part of the game - after the universe-eaters have swept past the monster-homeworlds.