I also feel lack of endgame applications. i even installed millenaire with sole reason to have something to use ic powers for
So, my ideas of Epic Stuff are mostly related to space
1. Artificial Sun.
2. Space rocket, taking player to another world. "Other world" can be generated same as standard, but with heavy tweaking of parameters different proabability of minerals and biomes, different lengths for days and nights, different sky, etc.
3. Player is making a settlement for settlers from another planet. kind of millenaire, except player do all himself, and settlers are spawning and despawning just like mobs, so they do not hog cpu, like millenaire, and player can decide what form buildings are (with some limitations). As a "rent", player get "space credits" that can be used to buy things, unavailable otherwise.