Here, I'll make it easier (and less expensive) for them:
Just transfer the multis for the Piano Concerto, and Pirates. Remix in surround.
Release that (plus upmixed Fanfare -- which btw sounds like it has maybe an overdub or two, and was probably edited) as the next surround ELP album.
Or, if they don't want to invest a lot, do a "best of Works" disc with Pirates, the Concerto, A couple from Greg's side (C'est la Vie and Closer to Believing maybe, toss in Enemy God and and Tank from Carl's side, then grab some stuff from Works 2 like BSS (the song), Father Christmas and a couple others.
But I'd rather just get all of it out there. It doesn't have to ben a big fancy expensive box, just all the music from that era.
And hey, I'll even give them a title - "The Whole Works"