I got information on Cassian Commonwealth.
Based on Wilderrun's journal on its "problems" (warfare, drought, and famine) and conflict on the rim, I think it might contribute to my Cassian (story but haven't played yet) background as a descendant of refugees from the Commonwealth and create a sanctuary until Dominion subjugated it (think a combination of Scotland, Kerensky from Battletech, and Game of Thrones' First Men). Even some Dominion defectors from that world disagreed on Exiles' glorifcation of the Commonwealth, other than ignorance on their pseudo-Gaelic culture. http://www.wildstar-online.com/en/stories/rise-of-the-cassians.html
The only indication of Gaelic influences really seems to be the accent. Otherwise its not really "Gaelic" there's no clan incorporation, though the Luminai could fit the whole archetype of the Sidhe plus the notion of warrior glorified leaders. But a lot of elements of Gaelic society aren't in the Dominion, its far too Anglo-Norman in influences. Including the glorification of duty.
Note the accents in Ireland are called Hiberdian-English, unless the person is a Gaelic speaker (which only comprises maybe 20% of the population) its not a "Gaelic" accent.
I added a note about the reactions to Dominus and subjugation of the outer Cassian colonies.
Space Opera, Mecha, Psionic-Techno / Magic, Planetary / Courtly Politics
Well, the background is fan-made (by me) and I added it to give a more sympathetic (or lean towards Lawful Neutral) for Dominion enough for new players to tolerate.
I use gaelic since I have two fan-made planets, a scottish and an irish one. The former is somewhat prosperous and more militaristic (Lowborns are generally well-educated then the ones from Cassus, semi-democratic where nobles had to gain support from lowborns, especially the member of special forces, and fortified settlements) but the latter suffered tragedies (lost their greatest ruler to ikthians or other evil entities, stoutroot famine, civil war, victims to Exiles' raidings for food and ship parts, but managed to get their back but not to the extent of their glory days).
But I possibly made it mary-sueish for the scottish one.
P.S- I am feeling that Lowborn Cassians might be behind in Dominion Hierarchy, based on Avra Darkos' report in Hycrest* and the lack of non-Cassians in lowborn starting areas (the one on the right where you got out of cryo chambers but closed off from other areas) of Arkship Destiny. That and one of Protostar's question in Hycrest ask about whether he or she is literate, which implied that many Lowborns are illiterate (or tried to pretend to be illiterate due to amounts of coporate red tapes).
*That actually didn't stop her from ordering the group to start a plague.