I would first like to say, I am really glad we found this map. It offers all sorts of story line ideas. My dungeon master brain awakens to the possibilities!
That being said, my brother in law Gavin is the guinea pig. He is a loyal space marine and I started him off with a small fleet (a Dauntless lance variant, 2 Cobras, and 2 Gladii). He and his crew woke up with terrible amnesia among asteroids and ruins. Eventually, he established communication with the Quantum Chevrons, a small Space Marine chapter who, while remaining loyal to the Emperor, has settled down on a massive rust bucket of a massive space port where they are in the business of repairing, buying, and selling ships.
At this point, Gavin (and his faction, of course) have reconnected with the Imperials of the Planet of Four Kings. For many years, the Planet of Four Kings has been thought of as a dead world after a fatal war with Chaos was over. The planet was left, nearly completely destroyed. Little did the Chaos know, the planet still had a large underground infrastructure where many Imperials took refuge and began to rebuild. Now, they have relaunched many repaired ships and recovered lots ones. The Imperials have been sent by Gavin who was hired by the Craftworld Eldar in the galactic north to bring them back Corsair Eldar ships (Battle Report 1). The Imperials brought back a few ruined Corsair escorts and a hulked Aurora light cruiser for the reward. Little did they know, they would be capturing a habitable planet in the process!
The planet was given to the Craftworld Eldar for the 1 remaining Ultima Battle Barge in the galaxy and loads of resources.