Looking over the maps from 3025, onward.
Two worlds on the spinward side fo the Reach definitively changed hands. Aea, and Regis Roost to the Taurians. They probably got Qalzi also. Artru and Katinka are possibilities, but lines never work in space. Brinton, which is usually the first system of the TC you visit, has been 'lost' which doesnt mean anything. The Rest of the Reach is lost also, so, nothing. Remember, the Inner Sphere considers all the Perphiery as Pirates and rapid surivialists.
Qalzi ia a recently colonised world, so Coromodir could have just not funded it any more, and the planet governement asked for TC help to protect it. Qazli was a money sink right now for the Reach, so its loss would not be that big a deal.
Aea is just as small population, so again, not much of a material loss.
Regis Roost is again a recently colonised world, with a fungi problem. Again, not much of a material loss.
Katinka is intresting. Not recently colonised, but does have a badly damaged ecosytem from some Mass Drivers targeting the planet, but seems to self-sufficient.
Then Artru, yeah, not much to say.
These worlds could be a swap between the TC and AC, with Lady Arano allowing those worlds to switch if they vote for it. TC gets to claim worlds where alot of hard work of colonising them has been done, and could offer the AC economic aid to even a MFN staus.
While the Coromodir would lose prestige losing those worlds to the TC, other then Katinka and maybe Artru, its not a another bodyblow to the economy of the Aurigan Reach.
Panzyr, Smithon, Tyrlon. Itrom, Guldra, and Coromodir are the core systems of the Coalition, and no one gets to claiming them. Fronc Reaches are close in the 3140s, but nothing definite. With the TC literally abandoning the recently colonized planets form the 3030s and 40s, some worlds could join the AC.
Now, i am just theory crafting the Coalition survival to the Wobbie temper tantrum. That is another brainstorm exercise. (Why did you do the Blake Jihad like that? (Shakes fist) CLICKYTEK!!!)