1.) The segments of Ghosts of Onyx that occur in 2552, take place after Halo 2. 2.) They would have no need to join the SPARTAN-IV program as they'e already augmented. Many surviving SPARTAN-IIIs did integrate into the Spartan Branch though. 3.) Micro Dyson Sphere wouldn't be accurate. Shield 006 was a literal Dyson Sphere. Like Blue Team, Katana was rescued, however, they are still stuck indefinitely in their slipspace pods..