Strengths: Characters belonging to the major faction's parent species have their posts count for twice as much in dominions, and have unlimited ally slots for members of the parent race in defending invasions.
Weaknesses: Characters outside of the parent species must have their posts count for half a post in dominions, non-members of the parent species cannot be allies in invasions.
I like this one a lot, however we could run into issues if factions designate their parent species as 'humans'. There have been a lot of human supremacist factions in the past (including the First Order and a lot of old Imperial factions), and since humans make up over 80% of the characters on the board, that could become a massive problem. However, for a low-played species like the Chiss (for the Chiss Ascendancy) or the Sith, this would be very balanced. Perhaps there could be some kind of stipulation restricting the kinds of species that factions can label as their parent species?