Well if I were to think about it, I imagine a merger with the Republic of the Sphere, not unlike that of the Rasalhague Dominion (given the continued presence of an exarch.
After that, we see a surrender of the Lyran Commonwealth, or at the very least that part trapped between the Wolves and Falcons. This is just a measure of practicality, as they've essentially lost faith in their government, and surrender to the Wolves is infinitely superior to being conquered by the Falcons. This gives the Wolf Empire the industrial capacity of the core Republic worlds, as well as the better part of the Commonwealth.
Next, war with the Falcons. The Jade Falcon clan will probably have to die completely. They arrayed themselves as the biggest immediate threat to the new Empire. The Free Worlds League is in a tenuous enough position that they might accept a diplomatic alliance (formal unification to come later). The Wolf/Falcon war might actually begin after the falcons attack the hell's horses in revenge for them backing out of their alliance. The Horses bend the knee out of gratitude.
The rest is a few decades of diplomacy, war, and assimilation.
Your thoughts are similar to my own:
1) Fortress Wall comes down, Republic comes out blazing.
2) During the fighting, Wolves repel the Republic attack and/or do a deep raid to take Terra and cut supply lines.
3) Wolves take Terra, becoming IlClan, take over the Republic and all but one Clan goes "meh...don't care".
4) That one Clan is the Jade Falcons and with a not level headed leader at the helm they do something stupid in anger at losing Terra to the Wolves...like maybe dropping nukes/weapons of mass destruction on Terra level stupid.
5) This act, whatever it is, enrages the other Clans and unites them against the Falcons.
6) Clan Jade Falcon falls to the other Clans and the Lyran Commonwealth capitulates as most of the fighting is in their territory/Wolf takes Tharkad with combined Clan forces to claim the throne for Alaric
7) Other powers, who have been fighting their own wars, get very nervous seeing this result.
This is where it gets tricky/mostly guess work......
8) Clan Wolf invites other powers to join the new Star League....FWL might join if given help in taking former worlds, FedSuns might join to beat off the Combine and Confederation, Heir to the Taurian throne might join if given help uniting their nation
9) The nations that don't join see the writing on the wall, but resist. Maybe the Clans smash one to make a point. The Combine is uniquely positioned for a big beat down. Confederation and Canopus submit, but plots behind the scenes.
10) Over time, through war and diplomacy, all nations merge and/or are conquered by the IlClan
11) Then 3250....or whatever year is selected happens...NEW ERA