I would like too see some sort of hardcore mode. It should:
Make you get more damage when hit
Slimes get hungry and agitate faster
Agitated largoes will turn feral (not just hunter largoes. All of them)
A 5% chance of an agitated slime to turn into a Tarr
Food grows slower and rots faster
Just being painful in general
And more...
This game mode would be made to turn this casual game into hell.