Cool ideas! A complex Sinbad style world may be too difficult to implement completely, as was said..
although I think most of the ideas mentioned by alaric could be implemented as scripted events. Yet I do remember some things happening in RPGs, even divinity itself that are like some of the ones mention here.
Most boars try to kill you in divinity but theres that one that doesn't...
The whole thing comes off as a scripted event though, the boar as very 'seperate' and unique from other boars, like he's not really a boar but a robot introduced by the game..
Perhaps if the screen didn't pause and he wasn't a different color and you had the option to kill him as you kill other boars (outside of a script) it would feel more like an event rather than a scripted event, and more like the boar was actually a helpful creature or just 'in the same class as the other animals but different'..
But I don't see why developers couldn't put more creatures in the game that aren't your enemey and that give your charachter something.
I imagine events like that would be effective in creating an enjoyable sense that anything can happen and that there are mysteries in this world.
They would encourage the player to explore and perhaps they would truly suprise him and create excitement or a sense of attachment to the world.
But esp. when they happen outside of a script and are in real time.