If players want to have a roster with Zax or Astra, they either have to make a roster from scratch or use a manifest. Extilior has Meat & Potatos so if Zax and Astra had something similar then they could learn how to use the other captains without having to learn the rest of the system and unit synergy at the same time. If manifests ever get removed from the game, it would give the player the opportuinity to engage with the other captains and even see them at all.
Good thoughts. I’m on it.