The Cornerstone of Your Prog Supergroup

After you name yours, I'd love to see your reasoning for such a choice.

My cornerstone player would be Tony Levin because: 

 - he can get along with anybody, 

 - he can play any kind of music (included among his over 500 albums, are diverse artists such as Paul McCartney, Paul Simon, Judy Collins, Cher, Alice Cooper, Buddy Rich, Lou Reed, Todd Rundgren, Seal, Gary Burton, James Taylor, Herbie mann, Sarah MacLachlan, Peter Frampton, Timm Finn, Richie Sambora, Dominique Vantomme, Peter Kater, Chuck Mangione, Larry Fast, California Guitar Trio, Al DiMeola, Phil Keaggy, Don MacLean, Lou Christie, Deodato, Kate & Anna McGarrigle, Phobe Snow, Mike Manieri, Melissa Manchester, Burt Bacharach, Ben Sidran, Laura Nyro, Art Garfunkle, Jun Fukamachi, Peter, Paul & Mary, John Lennon & Yoko Ono, The Roches, Bill Chinnock, Roy Harper, Kazumi Watanabe, Warren Bernhardt, Joan Armitrading, Johnny Warman, Jules Shear, Mark Knopfler (Local Hero), Gowan, Frida, Catherine Lara, Tom Waits, Marshall Crenshaw, Brian Ferry, Andy Pratt, Rosie Vela, Warren Zevon, David Torn, Jill Jones, T Bone Burnett, Robbie Robertson, Julia Fordham, Richard Thompson, Ringo Starr, Stevie Nicks, Steps Ahead, Laurie Anderson, Jeanne Mas, Claudio Baglioni, Phil Manzanera, Paula Cole, Chris Botti, Andy Summers, Eros Ramozzotti, Kevin Maxx, Magellan, Gov't Mule, Steve Hackett (Genesis Revisited), David Bowie, Willie Oteri, Michael Whalen, Eddie Jobson, Jakko Jakszyk, Nad Sylvan, Marco Minneman, Alec Sebastien, Phil Collins, Katherine Kaye, Jerry Goodman, Brandon Flowers, Steve Thorne, Sarah Brightman, Days Between Stations, William Ackerman, Slow Electric, The Weepies, Ólafur Arnalds, Steven Wilson, Goatika Creative Lab, Randy Vanwarmer, Lara Fabian, Steve Howe, Mike Portnoy, Gigi D'Alessio, Gibonni, Jordan Rudess, Niyaz, David Sancious, Ivan Lins, )        

 - he works well in the studio or live on stage (and has been touring almost continuously with an amazing variety of bands for the past 50 years including many of those listed above), 

 - he is a virtuoso musician (not just bass player) 

 - he is an incredibly adept and fast learner (has sat in on tours with Yes, Genesis, Pink Floyd, Sarah Brightman, James Taylor, Paul Simon, Richie Sambora, Ivanno Fossati, Carly Simon, Herbie Mann, Peter Frampton, Judy Collins, and many more)  

 - yet he is also very creative (is collaborative member of several outstanding bands, including Stick Men, King Crimson, Bruford-Levin Upper Extremities, Levin Brothers, Levin Torn White, Levin Minneman Rudess, Perfect Trio, and Liquid Tension Experiment as well as his own solo releases)

 - he has several very distinctive sounds (yet does not necessarily dominate the music, rather, blends in or helps create a very unique yet-always-interesting sound landscape)

 - LOVES music! (all kinds; is unafraid to try anything)

I much prefer Holdsworth as a sideman to a leader. I find his solo stuff way too self indulgent. He may have been too much of a tortured soul to lead a band.

Agree on the Levin solo material, I like it but its hardly ground breaking. Probably the ultimate perfect sideman.