This entry is full of spoilers for the Nostalgia chapter of Phoenix, so dont' read it if you haven't read Nostalgia.
So having finally read the Nostalgia chapter of Phoenix, I'm not at all certain how to interpret the character "Fox" who is clearly Black Jack in character design, though not in personality or occupation. What are others' impressions of him?
He seems to me to sort-of serve as a guide character completing the quest for the return to nature, which makes sense given BJ's environmentalism, but that alone doesn't seem enough to satisfactoraly interpret Black Jack's only appearance in Phoenix. Is this what BJ would become living in the degenerate world of Nostalgia? Is this what he would have been like without the childhood accident? None of these interpretations seem to really settle it...
On the other hand, Nostalgia certainly clarified why Hallelujah ordered Rock to exterminate the moopies in Phoenix: Future. A species with such ridiculously superior adaptability and survival skills makes the struggle for survival of all other races unfair, and its transforming ability (as Rock says) leads people to relapse into Nostalgia and abandon progress. As always, the different volumes of Phoenix clarify one another. Now the question is whether moopies are related to Ueko.