Yeah, but I want Prometheus Unbound. That was supposed to be on par with the Gothic Symphony. Since the vocal score exists and I believe that would include the piano orchestral reduction, maybe John Pickard could reconstruct it based on what he did with Vision of Cleopatra.
I think that might be the labour of a life time; I think John P should be allowed to carry on with his own compositions!
I wonder though, in the future, whether you could train AI to orchestrate. Ie write a program that orchestrates a piano score, and teach it how to do so in HB's style by feeding in HB scores from this period. I think it would be easier to do this and have a human orchestrator revise it than tasking someone with such a huge task.