In section 2.1 of the Indifference paper the reward function is defined on histories. In section 2 of the corrigibility paper, the utility function is defined over (action1, observation, action2) triples—which is to say, complete histories of the paper's three-timestep scenario.  And section 2 of the interruptibility paper specifies a reward at every timestep.

I think preferences-over-future-states might be a simplification used in thought experiments, not an actual constraint that has limited past corrigibility approaches.

This might just be me not grokking predictive processing, but...

I feel like I do a version of the rat's task all the time to decide what to have for dinner—I imagine different food options, feel which one seems most appetizing, and then push the button (on Seamless) that will make that food appear.

Introspectively, this feels to me there's such a thing as 'hypothetical reward'. When I imagine a particular food, I feel like I get a signal from... somewhere... that tells me whether I would feel reward if I ate that food, but does not itself constitute reward. I don't generally feel any desire to spend time fantasizing about the food I'm waiting for.

To turn this into a brain model, this seems like the neocortex calling an API the subcortex exposes. Roughly, the neocortex can give the subcortex hypothetical sensory data and get a hypothetical reward in exchange. I suppose this is basically hypothesis two with a modification to avoid the pitfall you identify, although that's not how I arrived at the idea.

This does require a second dimension of subcortex-to-neocortex signal alongside the reward. Is there a reason to think there isn't one?