Indeed it’s great that you’re digging into this!
Yes, my diagram was meant to be pretty abstract, so those excitatory and inhibitory arrows are not necessarily neurons (In fact, that whole scheme could be implemented by many unicellular animals). But for ancestral eumetazoans, with that ANS/BNS distinction, there is some specialization. The state control system roughly corresponds to the hypothalamus (or more precisely, its “terminal” or rostral segment), in which the signalling is primarily hormonal. That’s probably the case for the “tegmental neuropile” of lancelets, and of course our hypothalamus does a lot of hormonal control. In fact, chemical sensation might not even need “sensors” because chemicals directly influence metabolism and “downstream” systems as long as you have the right receptors in your membrane.
In any case, in modern animals neuropeptide Y (NPY) does appear to be a big part of a hunger signal, and the shift from locally exploiting to long-range exploring does appear to be governed by dopamine. Strictly speaking, originally it didn’t have to be an explicit competition, but rather a dopamine-dependent influence on how far you move before turning: As dopamine levels go up, you turn more, so you stay more local. Eventually, however, I believe the distinct needs of exploiting versus exploring motivated explicit specialization of different systems within the “peduncular” or caudal segment of the hypothalamus, which expanded into the telencephalon. Within it, the ventrolateral pallium (future piriform, insular, and neo-cortex) specialized for exploiting locally (learning local appetitive and aversive cues), whereas the medial pallium (future hippocampus) specialized for exploration (learning landmarks, odor gradients, etc). So at that point, some of those arrows correspond to neural circuits. And they make predictions - high tonic levels of dopamine should excite the ventrolateral circuits and inhibit the medial circuits.