I've been thinking about one of the main objections by readers to the plot of this series, and I think it's worth writing about it here since it's the most recent chapter and chances are a little higher that someone will read it.
The objection is that the protagonist has lost his purpose, and that the message of the series makes no sense. Some readers have said that there was nothing wrong with the mages' insurrection on the side of the Kadensha, since both groups have been harshly oppressed by Lavarta. Atrocities happen in wars and the resentment that fuels them is a lamentable side effect of the yearning for freedom.
Normally I'd agree, and I think the argument holds in the case of Kadensha. If you don't want dead civilians on your side, don't oppress the other side, it's simple as that.
But not so in the case of the mages. I think Aster and Zechs made a serious miscalculation when they decided to "make their own country".
Namely, that mages aren't a people.
Magecraft isn't hereditary. Mages will always be a scattered minority. Rebelling makes as much sense for mages in their society as it would, I don't know, for people with diabetes to rebel in ours. (I know there is a genetic component in diabetes, give me a break, I was just trying to think of something that isn't merely hereditary.)
The problem, I believe, resides in Aster's misinterpreting of the Epic of Sailama the Bard back in chapter 12. "The mages built a vast empire of magic" only makes sense if the roles were reversed: they were a dominant minority and oppressed the muggles in a class society, not a caste one. So what Aster is modelling his ideal after must have been an equally flawed society as their current one.
And all the indications that their thinking is flawed are scattered through the story. Rijitt has a muggle sister. Aster's parents are muggles, as were Zechs'. Even if mages were to make their own country, they'd soon be outnumbered by their own muggle descendants. The vein of guidance is a rare occurrence that shows up stochastically. There isn't a lynchpin connecting all the mages, they can be born anywhere.
And in fact, the agreement to supply mages and magecraft knowledge to Ermynn is even more dangerous than Fio thinks back in chapter 23: if magecraft is not hereditary, and if Ermynn has completely suppressed knowledge of magecraft to the point they can't even recover it, then… what are they doing to Ermynnian children who're born with the vein of guidance if they don't have the knowledge to teach them magic control? Ostracising them in ghettos is the least horrible solution I can think of. (Or it may be just a plot mistake. But I don't think it is, because Ermynn wants magic, not mages specifically, so I'm assuming they do have their own population of people with the vein of guidance but lack the means to train them.)
Aster and Zechs should be thinking in terms of class more than in terms of ethnicity. Peoples secede. Classes seek enfranchisement and equal rights.
Suppose the armistice is signed. What will happen to the mages? Will Kadensha become an autonomous country and offer refuge to all mages by granting them equal rights? Will Lavarta allow mages to migrate and lose their military leverage against the bigger countries around them? It seems Edgar can get his independence (and silver mines), but I can't think of anything in the deal for the mages.
So yeah, the mages are just fuelling more resentment against themselves with this insurrection. Even if the ones in the Rebel Army earn some respect and a place to live in Kadensha, these will be gains at the level of the individuals directly involved. But for all the other mages in the country who didn't join the insurrection because of their family or otherwise personal attachments, the insurrection has meant persecution and death, and a Kadensha-Lavarta armistice will hardly make things better for them - unless Aster can get measures for enfranchisement of Lavartan mages thrown into the deal. Given that Edgar doesn't need those to get what he wants, I doubt the Kadenshan side will lobby very hard for that at the negotiation table. In fact, throwing the mages (and Aster's neck) under the bus to appease the Lavartan side after the atrocity of Arka might sound tempting to Edgar right now. It might even have been in Ermynn's calculations.
I guess the resolution of this conflict will tell us how much thought the author gave to these issues.