Adding a endgame goal that never stops, that forces you to expand and explore constantly.

[bensin00]

The picture, that formed in my head of this was a hole that needs to be feed.

No idea how and why that hole existed, but the point is: at first it is like an endless chest, and you can feed things into it from 4 sides only.

But the hunger of the hole grows and at some point it is higher than you can feed into it. And when you cannot deliver enough the hole grows. So it becomes 2x2 big and while growing it destroys everything in some area around it. This needs you to build extra fast new belts and inserters around it, but now you can feed it with 8 inserters.

And so on! Next steps are 12, 16, 20 inserters.

But the hole grows and grows, the faster you are, the faster it grows. With it’s growth it destroys the near infrastructure which makes it extra thrilling...

Ye that would fit the picture. Cause you will somehow have to insert more and more into that hole. Or find other holes to insert into, so exploring would be a mandatory.