"Why was the Grey Council always to be found on a cruiser? Were they ever
located on Minbar itself? Or was the cruiser orbiting Minbar? Was it for
their protection, or secrecy? Or has this already been answered?"

We've hinted at it...the Grey Council always stays on its ship, being part of
the universe, giving it an exotic, distant feel for its people...as though
among the gods.

jms