Well, everything is fine. We recruit a couple of goblins - volunteers, buy a couple of females, breed a harem (if you can call it that), fеck that harem in all fields, an army is produced, with the help of which we begin to fеck (literally and figuratively) the nearest settlements. A normal game about management. For this, the cave that exists is enough.
An open world? Well, I don't know. Only if you make a completely new game on the bones of the old one (models there, sex scenes - all this can be transferred). No, this will no longer be a game about management (if the world is much larger than one, albeit not a small cave). So you will have to think a lot and rethink a lot. And you will need some kind of main character (most likely some kind of goblin, there are most of them in the game).
In short, for what the developer stated and what he set as his goal, a completely new game is needed, with a special concept.
And one more question - who will the rabbit produce? Its own kind or goblins again?