In the new "Tips & Tricks" it has a MMX5 strategy guide, and here is a rundown of the levels and the bosses names - they are named after members of the hard rock/metal band, Guns 'n' Roses. These levels have level names, like chapters of a book...unlike X4:
Chase the Truck!=Grizzly Slash (Crescent Grizzly)
Obliterate the Battleship!=Duff McWhalen (Tikal Whale)
Electric Trap!=Squid Adler (Bolt Kracken)
Fortress Lab Infiltration!=Izzy Glow (Shining Hotarunix)
Escape the Space Trap!=Dark Dizzy (Dark Necrobat)
Destroy the Time Bombs!=The Skiver (Spiral Pegasus)
Red-Hot World!=Mattrex (Burn Dinorex)
Into the Jungle!=Axle the Red (Spike Rosered)
Maverick Base Area 1=Rock Monster (yes, from the first MM game!)
Maverick Base Area 2=Robo Mask
Maverick Base Area 3=The Final Battle!=Sigma
Thanks Patty for the news!