I may not have over 5000 hours, but a difficult mode would be Fun.
More HP & attack patterns for bosses
Less resources
Nerfed Characters
Less food
Low food spoil time
Higher damage output from mobs
Faster overheating & freezing
New weapons ?
Ranged weapons ( not like darts but ones you control where they land with a lower craft cost, and have durability with required ammo )
This is very possible as it would act like the meteor blast from the forge.
Just throwing this out there,
But make the ruins a little bit more dangerous.