Hallelujah! These are discs I've always wanted even though I never knew they existed till reading your post. My deep hope is that Brian's magnum opus, Prometheus Unbound (which is also one of my favorite literary works since a kid) would be respectfully reconstructed and orchestrated from the extant vocal score which includes the piano reduction of the orchestra. If only I was a millionaire, I would instantly fund the effort.
I am not a particular fan of this.
What is your thought on Mahler's 10? To me, it is more important we have the completion because it is very different from just the first movement even if it might not be the final version Mahler might have landed on. It is his full draft respectfully constructed and I think these other scores should be approached the same way. Yes, it isn't perfect, it is the best we can do for now.