Alisha's DLC uses a different battle theme rather than any of the previous battle themes. This could have been done on the developer's part to give love to an otherwise-Advertised Extra, but the real reason? The original threebattlethemes are all remixes of Sorey's theme... who just so happens to be absent from the party for the entirety of the DLC.
It also gives insight as to why the melodies of original battle themes don't change as previously done in past games; it's because the themes were associated with a characterwho was always present in the party. Once you remove said character from the party, the themes disappear along with him, and you're forced to make something else to fill in the gap.
The fact that the Celestial Record says a Shepherd hasn't appeared in two-hundred years makes sense when you realize that Michael wanted to live the rest of his life in peace. Had he continued to write in chronological order and included himself, people would seek him out to use him for their own purposes, which is exactly what Sorey has to go through on his journey.
The noble family not being present save for Alisha actually makes a lot of sense when you think about the state of Hyland. Hyland is being run by the Senators and the nobility is more or less In Name Only. Alisha though actively tries to be involved as a knight and princess despite this. Of course the nobility isn't shown in game; they hold no power. Alisha has to work to be involved, hence why the nobility is absent.
Actually the members of the council are also nobles, Maltran is also a noble, you come across a handful of Hyland nobles throughout the story, and the real reason why see more nobles is simply because as Lailah points out multiple times Sorey can't help everyone, there's literally no reason for Sorey to meet them on his own, so he doesn't, and Alisha also plays a part in Sorey not meeting them either. As character's point out multiple times in skits the other nobles don't really get along with Alisha, so she has no friends amongst the nobles, so there is no avenue to allow Sorey to run into more nobles. This is also the reason for Alisha's lack of political power. Alisha despite the fact that she makes it seem as though she's involved in politics by way of being a knight, in reality that couldn't be further from the truth, Alisha actually doesn't like being a princess and so she has a tendency to shirk her duties as a princess in order to be a knight. This results in her simply not being around the political sphere long enough to make a difference since she values being a knight over being a princess, this results in her frequently choosing her knightly duties over her duties as a princess. All of this amounts to Alisha not actually having much of any political presence because she's chosen to be a knight.
The above explanation works to explain all of Alisha's character including why she ultimately couldn't be Sorey's squire. At the beginning of the game Alisha makes the claim that she doesn't have any political power because she's actually more akin to a lower class noble, but that claim doesn't make sense that she quickly rises in power in the latter half of the game, despite not having the council on her side. This doesn't match up to Alisha's claim about her not really having any political power on her own, until you consider the fact that Alisha doesn't like being a princess, and so was likely looking for excuses to ignore her duties as princess. This actually explains Alisha's lack of political power, since even powerful kings need political allies in order to rule, but Alisha was hated being a princess and so didn't care to make any political allies, and her confrontational attitude towards other nobles didn't endear her to them either. So if Alisha was lying to herself the whole time, why didn't she become a hellion? Because Alisha genuinely believed it.
Alisha quickly gains political power by the end of the game, even though the council is still against her, this seems to come out of nowhere, until you remember that one of Iris Gem quests, where Alisha jumps to conclusions and ends interrupting the meeting between a Hyland and Rolance politicians who were planning on forging peace between Rolance and Hyland, said quest ends in the Hyland politician he effectively blackmailing Alisha. At the end of the game we find out that Alisha on the order of this politican has been currying favor from the nobles an act that Alisha would have been against at the beginning of the game. This is a full 360 until you realize that Alisha probably started currying favor from the nobles because the Hyland politician blackmailed her into doing something that Alisha would not have done herself, like say, forcing Alisha to do her duties as a princess. Due to the fact that Alisha is the princess and she now has political allies she was able to gain a lot of political power and influence.
It goes further than that, said blackmail is also why Alisha didn't became a hellion, despite Maltran's betrayal and her revealing that she set Alisha up to fail, by making her obsessed with being a knight. It's because Alisha being forced to act like a princess and actually seeing results from it resulted in her realizing this but being unable to admit to it because to her idolizing Maltran and the stories of heroes too much. Maltran's reveal resulted in Alisha losing the last vestiges of her hero worship towards knighthood, as the one thing that she used as an excuse had dried up, and she was being forced to admit something that she herself had realized and believed, and thus made Alisha finally prioritize being a princess over being a knight.
As pointed out by some fans, Maotelus's shrine was supposed to have four other Seraphim that had assisted Maotelus, yet when the party arrives at the shrine, there are no other Seraphim. There are, however, four powerful Hellions of different elemental types across the shrine, with each one following the Elemental RockPaperScissors that Edna explains to Mikleo. One would have the right to believe that the four Hellions the group fought were really the four Seraphim that were supposed to be at the shrine.
If you defeat the Final Boss ahead of time, you unlock the Bad Ending, which shows The team sitting in a cottage, with a storm raging outside. After a few short conversations, the camera cuts to the outside, where we see a large monster looming outside. This left many players confused, as there is no explanation to what is happening. However, once you reach the end-game, you find out that by defeating Heldalf, you unleash Maotelus, the most powerful seraph of all, who is deeply corrupted by malevolence. Since the party doesn't know that Heldalf was bonded to Maotelus, by defeating Heldalf ahead of time, you unleash Maotelus on the world, probably leading to even worse natural disasters and hellions than are already present in the game. Nice Job Breaking It, Hero!.
And then Tales of Berseria provided even more context. Maotelus being unleashed on the world isn't even the worst part; with him corrupted and no longer balancing the amount of Malevolence around, the world is in an unstoppable death spiral.
Imagine being someone who has strong enough resonance to see hellions. Imagine being surrounded by monsters, and since a human having high enough resonance these days are rare, you are possibly the only one who can see them within your area. Makes you wonder how many people are written off as insane when they scream about monsters that nobody can see because that person is the only one who can see them. Unless a seraph comes along to explain everything to you, makes you wonder if they are willing to help as it seems like a lot of seraphs have low opinion on humans or need some convincing to help humans, or another human with high enough resonance comes along you might spent the rest of your life convince you are insane or be terrified of seeing monsters all around you that nobody can't see and become mad.