The voting body will never be hard enough to fully take the grimdark path. Any attempts will be half-hearted and met with failure in the end. Only real choice we have is to be multikult now. Shifting mode from Imperium to Culture.
***
Considered course of action:
Attempt to engage Raumen help in brokering a ceasefire with the Hin'in by any means necessary.
Creation of a new Federation with greater autonomy for worlds and factions.
Attempt further contact with Turanei and Hin'in for multicultural exchanges.
Offer our AI technology as a gesture of goodwill.
Reasoning:
We should not declare a ceasefire unilaterally. That would not help in gaining Raumen trust - again we are acting on our own interests. What we should do is send our diplomats to the Raumen and inform them beforehand that we are planning to negotiate with the Hin'in for both quarters to pull out and create a demilitarized zone. If need be, we will apologize for interfering in their civil war and provide reasonable reparations that we can afford. We may offer interested Raumen clans membership in the Federation, or alternatively offer to help create a 'New' Raumen Confederacy with partnership in the Federation, where they are offered more control in their interstellar policy and nearly full autonomy militarily, as well as favourable trade conditions.
Next, with regards to the Commonwealth we have no choice but to offer peaceful re-absorption with greater autonomy. To sweeten the deal, military ties should be in the form of a pact, ala NATO. They will be allowed to raise their own military forces. We will still maintain control over interstellar policy, within reason. This will be subject to the successful formation of the Federation, of course. I propose should the idea take off, and the Barbarian continues with this experiment, we collectively debate and draw up a brief 18-point (or so) charter for the Founding of the Federation.
Contact with the Turanei is strongly encouraged, while if a ceasefire with the Hin'in is successful we must also approach them to rebuild both our battered empires. We can learn plenty from them.
Economically, I am hoping our overtures of friendship to the Raumen will help recruit their expertise in our recovery. Again, as mentioned; by all means necessary.
Therefore I propose sharing our AI with every race we know as a gesture of goodwill.
edit: I feel that the current name as proposed by heechee1, the NPFR, is perfectly fine and expressive, but I strongly suggest that we consider the acronym NCR as an alternative.