Requesting massively resource intensive endgame level contruction projects (hundreds of resources required).
-Could be low hanging fruit (we’re mostly just spending more time with your beautiful crafting system that already exists!)
-Could be optional so as not to disrupt the pacing of the game’s story/progression.
-Would extend the game’s life post-story
-Ideally, there would still be a reward, story or otherwise, to motivate completion.
Random examples: repairing titanic alien structures. Building of a starship. A phase gate