How does this look for a more balkanized Inner Sphere?
The Terran Free Republic (TFR) formed in the wake of the Terran Alliance (TA) collapse following the Outer Reaches Rebellion. When House Cameron formed the Terran Hegemony (TH), there were many who didn't like the way it was shaping up. These people would go on the form the Terran Free Republic.
With neither nation compatible with the other, war was the only outcome. The war started in 2321, when the TFR laid claim to Terra and the Hegemony, and the TH responded in kind. By 2351, the war was still inconclusive, and while the TFR had yet to seize Terra, they had managed to savage the Hegemony Armed Forces.
It was a stalemate that resulted in an uneasy peace, spurred on by the growing strength of the neighboring states. When the Draconis Combine and Lyran Alliance launched raids into the Terran Core (the space around Earth) the two former enemies became suspicious allies.
When the invasions ended and the to exhausted nations turned their gaze once more upon each other, the TH had a plan to reduce the TFR's power. They instigated a separatist movement in the Sirius, Procyon, and Graham systems. Since these worlds had once belonged to the TFR and didn't want to be part of the TH, they became the Sirian Concordance (adding Pollux as well).
The TH followed suit by setting up the Northwind Hold, the Duchy of Small, and the Zosma Protectorate. By the time the TFR realized what was happening, it was too late. However, this organized effort would not be a flawless process for the TH.
As a result of the support for secession of former TFR worlds, many TH worlds decided they wanted out as well, forming the Covenant Worlds, Shiloh Alliance, Federation of Skye, and Galatean League. Unable to handle so many systems leaving all at once, the TH was cut to size.
TFR leaders then proposed a new league to keep outside invaders from attacking the now weakened core (and prevent the TH from trying to annex the separatists. Unable to refuse, the TH agreed and the 1st Star League was formed.
When the Star League formed, it proceeded to conquer all the nations that refused to join willingly in a much larger and more scattered Reunification War. Over the next 200 years the Star League kept peace as best able, but when tensions between the TH and TFR began to rise again, it began to lose stability.
First the Federated Suns, then the Draconis Combine erupted into civil war, with the Federation of Varney and Alliance of Galedon attempting to break away. With the Star League Defense Force attempting to quell the unrest, the League was caught unprepared when the Federation of Skye's House Kelswa began a succession crisis that saw it shatter almost entirely.
The economic and political aftershocks of these events spread unrest and civil disobedience across the League, which many nations took advantage of. At this point it became clear that a cabal of nobles, led by Stefen Amaris of the Rim World's Republic, were actively trying to usurp the League by distracting it's defenses in these civil wars.
However, the plan began to back fire as it became clear that many smaller nations were tired of League oppression, and more fractures occurred. Like a window of glass, once a crack starts it can only spread further.
With the SLDF being annihilated on all fronts and even the cabal of nobles losing more and more power, the High Lord of the Star League, Richard Cameron was murdered by Stefen Amaris. This led the Terran Free Republic to invade Terra, where they tried to capture Amaris, only to get attacked by the remaining SLDF.
With the centralized government beheaded, all hell broke loose and in 2780, what would be called the Great Fracturing War raged across the Sphere. By 2866, many nations, now tired of war, worked to bring peace.
At that point, the same amount of technological loss as the first two Succession Wars had taken place, and the remaining SLDF had fled and created the Clans.
For the next century, the 3rd Succession War's small border and brushfire wars would occur until the Signing of the 2nd Ares Conventions, which would bring a new era of peace. In the center a new Star League began to form from the smaller nations in the core.
However, tensions remained high since no conclusive victories were had by any nations. By 3025, the maps is as it looks now.