Itsuki's lightning magic may seem to be a random choice at first until you remember Chrom, his Mirage, is best friends with Robin, who is known for his/her lightning magic. Considering that Mirages are in an endless war, Chrom probably picked up a few things from his friend or learned it as a sort of tribute to them.
It's also a partial shout-out to Yu Narukami from Persona 4, in that Yu's mascot persona also uses electricity-based attacks. (That and how Yu in the anime version is also a Chick Magnet.)
While Eleonora's level upon joining the party is roughly in the range of your party (about mid 20s), her Stage Rank is likely significantly lower than the party's. Considering Stage Rank is a reflection of how one performs, why is Eleonora's so low despite being a senior member of Fortuna? It's because she's not that good of a performer yet. This is shown by the poor ratings of her show, Dandelion in Love, and the lack of job offers she receives. She eventually becomes good enough to have a lead in a Hollywood production.
Navarre and Caeda's promotion options reference both the original Fire Emblem: Shadow Dragon & the Blade of Light and Fire Emblem: Mystery of the Emblem games (where they could only promote to Hero and Wyvern Knight respectively), and the DS remakes (where the Falcoknight and Swordmaster classes were added from later games).
One of Chrom's promotions is Conqueror, a class from Fire Emblem: Awakening that was unique to Walhart, an antagonist and enemy of Chrom. So why would Chrom have his enemy's class as a promotion? Because Awakening points out how Walhart and Chrom are not so different in their end goals of uniting the world, just in their ideologies of doing it. Conqueror!Chrom represents how easily Chrom could be like Walhart if he ever decided that Might Makes Right.
Yashiro helps Excellus in his boss fight without much second thought, and agrees to join the party immediately after. But remember that Navarre, his Mirage partner, is a mercenary (not the class... well, not the class anymore). He's used to fighting for anyone who'll employ him, regardless of ethics. (He becomes an enemy again in a bonus chapter from Mystery of the Emblem's remake and has no qualms fighting his former allies, for one.) By defeating him, he essentially saw Itsuki's party as the higher bidders. This is also reflected in how Yashiro approaches acting, taking on any role he can get.
Why is Cervantes the boss of Tiki's final sidequest? Because he was also the boss of the chapter where you first meet Tiki in Awakening.
Doubly so since Tharja is heavily implied to have been Rhajat in a previous/future life.
Touma and Ellie's Vitriolic Best Buds relationship makes a lot of sense knowing her Mirage is Virion, given how his interactions with his game's Cain archetype, Sully, started off.
Marth's role as the 11th-Hour Superpower goes deeper than just his relationship to Medeus. Recall that our main hero specializes in Thunder magic. Medeus is an Earth dragon. Now, when electricity and earth clash, which element typically winds up on the losing end? No wonder your party needs a boost.
Bord and Cord's role as the bosses of Kiria's final sidequest is more than just another cameo: they also serve as this game's incarnation of the recurring "comic relief Axe brothers" archetype.
Itsuki has the power to destroy certain walls found in dungeons. And it's no wonder Itsuki has that power: his Mirage, Chrom, was known for accidentally knocking holes in walls in his home game.
Itsuki's wide range of skills that's available to him is more than him just being a Jack by virtue of being The Hero; it also reflects the fact he's tried every part of the entertainment industry due to not knowing which role he prefers.
As the Guide Dang It! mentions, there is a Duo Art that can only be earned if Itsuki and Tsubasa improve their relationship. Simply, you have to earn 30 "affection points" out of a possible 50 through side stories and dialogue options. However, these points aren't mentioned at all, nor are you notified when you've earned them. Why? Because Itsuki is Oblivious to Love! Since he wouldn't notice Tsubasa's growing feelings, and not even her initial crush in the first place, the player wouldn't know it either.
Out of all the characters in the game, the main character is a Supporting Protagonist who rarely ever sees the stage. That being said his guidance and support is paramount to everyone's own arcs as they grow in their own roles. And as any good director will tell you, "There are no small parts, only small actors".
Mamori is notable as she has no Ad-Lib skills. That's because she's a child star for a children's cooking program, there's no real need to improvise.
In the same vein, Kiria only has one Ad-Lib skill. Gameplay-wise, she doesn't have a true weapon, using a microphone that acts as a traditional staff. In addition she's classified only as a singer, thus the only thing that gets improvised are her songs represented by her blizzard spells, for example in case of technical error, she can overcome it with an acapella version of her song.
Touma has a garbage Magic stat, but fortunately, almost all of his moves are based on his physical attack - even the elemental ones. Of course it does, since the form of performance art he derives his Performa from is Toku, which favours practical effects and athletics over excessive post-production. Particularly the stage show form, which he starts his career in. There's no "editing magic", he does all his stunts in person!
Kiria's spell list early on favors blizzard spells. By the end of the game she picks up wind spells as a secondary element both as spell and session skills, and while she can learn fire spells as well, they aren't as prominent as her wind spells. Kiria shares a lot of screen time with Tsubasa often times learning off of each other, in fact learning Tsubasa's cute charm is a key part of Kiria's development, naturally speaking, she would pick up Tsubasa's wind element as a result.
It might seem like a case of Gameplay and Story Segregation when Mamori joins the party at a level on par with everyone else when she only became a Mirage Master a short time ago. However, Mamori is the inexperienced one here; Draug, on the other hand, was Barry's Mirage for years, and still has all of the memories and experience associated with that time. It's likely that he's the one taking the lead and showing her the ropes until Mamori is skilled enough to handle more fights on her own.
Asides from the two listed above, every character has two Ad-libs based on their weapon and signature element. Not only do they represent their various roles through their various side stories, but they also represent that character's growth or skills.
Itsuki's Ad-libs are Back Chorus and Firm Resolve using lightning spells and sword skills respectively. Back Chorus represents his early time as either an extra or just a supporter for his friends. Firm Resolve is a true representation of Itsuki as a leader of Fortuna Entertainment using a sword that signifies him as the leader and eventually becoming its President at the end of the game.
Tsubasa's Ad-libs are Tsubasa's Kiss and Fly: You're My Wind using lance skills and wind spells respectively. Both Ad-libs showcase her growth during the game, first as a rising star and then as a break-out celebrity. Because you are encouraged to utilize her wind spells proactively, one can say that she always had the potential to become a huge star.
Touma's Ad-libs are Raging Stampede and Ouga Flame Thrust using lance skills and fire spells respectively. Being in a live action super hero show means that Touma has to show off more stunt work than simply act. Raging Stampede shows him portraying a villainous monster who only knows how to use his basic fighting skills, thus it's Ad-libbed with his lance skills. When he gains the role of Masqueraider, the heroes use more explosive effects, thus his fire spells are used to fuel those explosions.
Eleonora's Ad-libs are One-Sided Love and Arrow of Destiny using bow skills and electric spells respectively. Rather than being about growth, Eleonora's range is on display here. One-Sided Love displays her skills as a romantic heroine, a straight-forward role that has her act like a love-struck youth. Arrow of Destiny displays her skills as an action heroine, a more electrifying role that requires her to act more dynamic as a hardcore badass.
Yashiro's Ad-libs are The Hungry Man and Operation using sword skills and fire spells respectively. Yashiro, who is already a successful idol and entertainer, is only expanding his range of roles. Thus his skills are more about using his abilities in a different way than he is used to, either reacting to food in an over-dramatic way, or to become a villainous character fighting a super hero.
The fact that the mirage incidents have been happening for years. Just how many people were kidnapped in that time? How many people had their performa drained and were killed like the idol Azusa?
Kiria was operating on her own long before the others joined Fortuna, so how effective was she? It's shown that they haven't been able to save everyone, such as it was with Azusa, so how much baggage has Kiria been carrying around on her own?
The intro cinematic shows an entire opera house of people being snatched while a 13-year-old Tsubasa watches on. She was there watching her sister. What kind of therapy did that kid have to go through to bounce back as a Genki Girl years later?
The same could be said for Yashiro, but his damage is much easier to see.
What did the mirages make their victims do after possessing them? When you find Aya, she's barely wearing anything at all. Was it just a preference by her captor, Aversa, or was there something more sinister happening to the victims?
Even worse, sometimes the mirage victims can be children.
The dark side of the entertainment industry is almost NEVER shown. What if a molester head honcho gets his dirty hands on Perfoma power to partner with a Mirage?!
