So basicly, this force, how should I explain hmm.... A little change:
To the rest of Sirius this was intolerable. The state of affairs was hectic enough as it was. They had suffered only recently from Nomads and the widespread panic over the possible return of the Coalition. How could a remnant army come so close and be rallying dissidents against them at a time like this? House cooperation in the frontiers had proven successful in bringing relative peace and prosperity before. It would do so again. Beginning work on a new generation of naval forces, the colonies merged these high-tech assets into a Sirius Alliance Star Fleet. Integration of forces would take time... but ultimately benefit Sirius.
So I'm sure since the Houses are very weakened, they'd kinda have a last hope, a group which would defend them from the outside, looking it from Discovery Lore perspective, they'd use this as a benefit so in case they'd be attacked from the outside, they'd have a trusted force which would deal with it and this way they can still continue what they were doing all day long. But of course a unification is mentioned... But not all Houses might agree to it, however, they might agree to that, to form a fleet to fight the outer sectors and outer threats. Of course this just applies for the Houses, but the Sirius Alliance would still insist for the real cause of the unification and to end the remnants army.
