The Galactic Alliance is formed by the New Republic + other additional factions. The Confederation is a rebel faction from the Galactic Alliance formed by several important factions or sectors, Corellian, Bothan, Hutts, Corporate Sector, Fondor and more.
In that war, there are light and dark factions with characters changing of faction and many many good battles descripted at several books.
That story is the main reason because I have added these two factions. I have recorded a video, there are several things under development or unfinished but you can see the Corellian Dreadnought, the differences with the Rebel faction which it is the origin from both and what is the main idea, at least at skirmiss. In time, there will be a complete GC with both factions.
For the record, the Rebel Alliance can build the Corellian Dreadnaught as all the Confederation and Galactic Alliance units. There will be heroes but they will be exclusive from these factions.
Getting some Battlestar vibes here.
As the rebels, how would we be able to get our hands on the dreadnaught in game?