I think a good idea is:
"giving each faction a legendary slot for famous ships like the planetkiller, Space Hulk, and all the other named ships among the other races.
It could be done one by one with small dlc's. ("The-legendary-Ship-dlc-of-the-month"
In the end, when the balance and point costs are well done, it could give more ship-choices for the players without creating ships that dosen't exist in lore.
Implentet like the demiurg without crew and favors, (Abbadon's favor is just "Black Legion" for example^^).
the legendary slot could named. "Commandoship or Admiralship" or something similar.
And we could increse the levelcap for the players from 8 to 9 to unlock the famous ship slot.
(or maybe 9 for the Grand Cruiser Slot, and 10 for the legendary Slot.)