Yes, losing of capital means something only if you not made way to retreat and didnt evacuated most of thing somewhere. In WW2 russians had plan if all going very bad, blow up Moscow and hold on Volga with Samara as new capital.
There btw another important thing, for all historical examples exist very strong motivation - was well know that invaders will remove kebabs civillian population, so there was choose between removing and being a thing. Imperial ambitions worked rarely and for short conflicts.
What motivation from Gallic and Bretonia side? I guess that moment mostly screwed, disco haven't enough propaganda, goals of population, which bread they eat every day and etc.
P.S And yes, zoners have population of small city on Gran Canaria, nobody cared much, all interested parties already in that conflict, so i dont see what should change. Also there is bad dark cyberpunk distopia, and also. Bretonia. Queen. IMPERIA. Conquest and annex something when you have imperial/monarchy mental peoples always good for ratings.