Had an idea that was a bit of a spin off from the story idea proposed.
The Star League has Fallen. Kerensky and his Exodus find a Mass Relay farther beyond the deepest of the Periphery. There they meet the Citadel races through an Asari Science expedition. Kerensky is quick to open talks and establish the Star League in Exile. And they are allowed to come through the Relay and settle within the region of the Attican Traverse. With some aid of the Citadel they establish Eden Prime and a number of other colonies within the Attican Traverse and expand. Due to having rebuild politically, economically and militarily, and with some assistance from the Council, this new society isn't a Star League in Exile but becomes a true Alliance of Systems. Or systems Alliance. A Mix of modern day Democracy and some of the old Neo Feudalism of the past. 300 years go by before the Alliance is ready to move back into the Inner Sphere. Time period is 3050 for the IS and maybe a century or two before the Reapers.
Several story plots.
* Human/Alien politics. Earth brings unique technologies to the equation and the Citadel wants them. Badly. The Star League in exile is willing to trade for numerous concessions.
* The Rise of BattleMechs. Turians take to BattleMechs like a fish does to water. Soon other races are looking to adopt their own designs, but its clear that Human designs trump all.
*The Alliance has been sending missions back to the Inner Sphere periodically to determine what is going on. They've also been funneling people out of the IS who could help rebuild their society while also bolstering population numbers and genetic diversity, though Clan style Birthing tanks are also used as well. Scientists, engineers, anyone who wants to escape the madness of the succession wars who can contribute anything they'll take them and their families.
* ComStar becomes aware that the survivors of Kerensky's exodus are still involved in affairs of the Inner Sphere. Comstar seeks to learn more.
* The Alliance has rapidly advanced technologically while the Inner Sphere is mostly recovering their Star League era technology. For the Alliance we are talking a perfect blend of Clan tech/Mass Effect technology to give the Alliance a terrifying edge militarily. Naval gauss rifle tech combined with Mass Accelerators. Improvements Naval and Ground PPCs and Lasers, artificial gravity and inertial dampening systems (thanks to eezo) and finally, making serious breakthroughs in jump tech that gives them NBSG style jump engines. At least in terms of capabilities.
* Turians have been agitating for the Alliance to fix the situation for decades by the time of the main story. More than a few instances of the Turians about to do it themselves only for the Alliance to step in and stop them. This has nearly resulted in war between the two on at least two occasions.
* The Inner Sphere becomes aware something is going on when Alliance ships appear in the Inner Sphere and begin opening communications.
*FedCom/Alliance political squabbles. Hanse Davion is not going to give up his dream of seeing his grand children and great grand children sitting on the Star League throne. Relations with the Alliance are amicable but the FedCom sees itself as the true inheritor of the Star League legacy. Not the Alliance. Combine, Capellans and even the Free Worlds League are even less receptive than the FedCom.
Batarians find another relay that opens near Combine space and decide to invade. Draconis Combine must now deal with regular slave raids and attacks on its territory by the Batarian Hegemony. Combine begins devoting massive amounts of resources into building warship fleets to hold off Batarian attacks...which forces the other houses to do so as well.
With confirmation of aliens now known to all, and with Batarians actively attacking human space and infact increasing their attacks, Human attitudes shift based on these new facts. Comstar calls for a Summit on Terra and invites all the great houses and even the Periphery states and the Systems Alliance.
New Star League is proposed and accepted with Hanse Davion crowned the new First Lord. Victor takes up the reigns of the FedCom. The Capellans and the Taurians do NOT sign on with the new Star League accords. The Systems Alliance also does not sign the accords. It should be noted that the title of First Lord is not one of heredity but elected by a Council of Lords and then ratified by a Senate. A sign that this new Star League has more democratic leanings than the previous one.
Davion gets straight to work internally and externally and institutes rapid reforms. His goal is to see Human space safe, secure and prosperous. To that end he makes an alliance with the Systems Alliance and then opens negotiations and trade with the Citadel. Internally he promotes peace and trade among the great houses and the Periphy and shocks many with making a true peace with the Draconis Combine and the capitalizing on that with a treaty of Peace with the Taurian Concordat. Free Worlds League proves more of a challenge but are at least receptive and willing to talk. Hanse Davion becomes known as the Peace Maker 1st Lord. And it is largely through his efforts that things within the Inner Sphere finally stabilize.
*Batarians realize that if Humanity unites against them they'll be hopelessly outmatched. Terrified of what this means they resort to do something drastic and stupid in the hopes of killing the Star League in its infancy. They find a way to bypass Kurita space and hit Terra directly in the mother of all decapitation strikes. Hanse and Melisa Davion are killed as are over 50 millions people in a surprise attack. Star League Defense Force and an Alliance Naval squadron in the area engage and defeat the attack in detail.
*Theodore Kurita is named the new First Lord of the Star League and continues many of Hanse Davions reforms (He dares not touch them because they work). But where as Davion was the 1st Lord who brought peace. Kurita is the one who will bring the Star Leagues first war to an Alien race. Under Theodore the Star League expands its alliance with the SA and begins a massive military buildup thanks to new treaties of technology sharing with the Systems Alliance.
*The Human/Batarian War. The Systems Alliance and the Star League declare war on the Batarian Hegemony. Star League and Alliance Warships pour over the Batarian border like a Tsunami over a coastal village as they conquer world after world before Karshan eventually surrenders.
*Citadel Council politics. They are concerned about the juggernaut of Humanity. There is talks of inviting Humans to the council.
*Story ends with Kurita paying the first state visit to the Citadel on behalf of the Star League.
Thoughts?