I am not sure that Steven is the right person to do Frank Zappa.
His work on many of the other "progressive" albums were, not that good.
If we're talking dusting things up a bit, so the sound is cleaner, I'm OK with that. But simply manipulating levels and combinations of instruments is nothing more than what any other conductor did to anypne's music for hundreds of years, and you might prefer Karajhan a little more than Wilson, but i'll take Stravinsky doing Stravinsky or Berntein instead because they know it is less about the volume of this instrument or that instrument than it is about the WHOLE of the piece of music!
At this time, and his solo work is very clear on that, he is just on his pig'ging along on his smarts and talent and basically tell his mates that they are not good enough musicians to play with him any more, because he can make anyone playing for him, sound better than his own band that he is bored with! And his ego is way bigger and he's not going to lower it for a "band".
I also think that Steven is very good with a rock band, because there are only 4 or 5 instruments to worry about, and "ambience" for rock'n'roll pieces is not a requirement and most top ten ignores it in lieu of lyrics ... something that Steven is learning really well about these days!
To trust Steven with music that is ... almost exclusively designed as an orchestral arrangement, is something I would NOT DO ... EVER.