You can see the Angel and Guristas arcs in the Agency window, however they both only show a single agent to speak to in order to start them.
With the upcoming ability to align yourself to a pirate faction people are wanting to increase their pirate standings, and only showing one path to starting the epic arc may discourage people from doing them if they feel it would be too much work to repair their standings with the empire faction that Arc elects to display.
Arc should indicate which factions and corps can be used to start the pirate arcs and give the player enough information to figure out if they can do it and where they need to go to start it, rather than hiding half of the mechanic from them.