Just give quests their own invisible hunger bar

[Tamalak]

Reward is multiplied with whatever "hunger" level you're at (300%, 75% whatever)

One medium sized quest consumes like 100% hunger, others consume more or less proportionally.

There you've fixed no-lifer questing while also making it rewarding to casuals.. you are welcome..

[DPblH]

They are already works same way.