Here's a random concept for FE representation. Get your pitchforks and torches down, although you'll be picking them back up soon.
First, the cuts, to get the bandaid ripped off: Roy, Ike, Lucina, Corrin and Chrom. All of them are due to redundancies with era representation with the newcomers I am proposing, as well as to cut down on potential bloat. I know Ike and Roy are the most popular two male FE characters of all time but Smash played a big role in that anyway, and same goes for Lucina. Corrin is the only one who is also spite. If I somehow have extra time and resources, or if I can when DLC rolls around, the order I'd bring them back in for the uniques are Ike > Roy > Ike updates > Roy decloning + updates > excess newcomers (up to and including other characters from Fates) >>>>> Corrin. Chrom and Lucina might be demoted to alts of Marth unless time is going well.
The veterans remaining are Marth, Robin, and Byleth. Marth can remain pretty much as is although I would like to see more alts (FE1 Marth, FE3 Marth, Lodestar/King Marth) and maybe we can find a way to sneak in the Geosphere as his new Down Smash, or for an alternative FS he could pull out the Binding Shield and have it do that dragon killing thing but on the other fighters. Robin has one change: for reasons that will become clear later, Nosferatu is removed completely, and in its place is Fimbulvetr (imagine an icy tornado swirling around Robin for a few seconds, which would be a passive attack option); perhaps an alteration for the FS to include multiple Awakening characters or just Morgan over Chrom. Byleth is as is, although I wish their FS was just Sublime Heaven, and I wish there was some way to incorporate Divine Pulse more creative than a counter (albeit with the 5 cuts, that's 5 less counters, so maybe Byleth can squeeze one in). Marth represents the basic lords, Robin anima magic, and Byleth the weapon triangle + bows.
The newcomers are Elincia, Lyon and Julia. These three further build upon Fire Emblem representation by taking a focus on certain concepts and ideas in the Fire Emblem series by focusing on the units other than the main protagonists. None of them are irrelevant to their games, either.
Elincia (while reading this, listen to this:
Bearer of Hope from Radiant Dawn), from Path of Radiance and Radiant Dawn (same games as Ike) represents staves, skills, mounted units, flying units and even the obscure mechanic of dismounting, having two fighting styles based on whether she's riding her pegasus or not (that's not a thing in the Tellius games, but she's where it goes), and even unit death, as well as representing Tellius and the GCN/Wii games. To elaborate on the dismount system, she would mount her pegasus with her dismounted up special and dismount with her mounted down special. The pegasus has a lot of perks (high weight, higher speed, stronger attacks, a fantastic recovery) but also plenty of weaknesses (largest hurtbox in the game, no dodges, inability to grab, inability to grab ledges, inability to pick up new items) and her pegasus also has its own separate HP stat that when it reaches 0, it dies, and Elincia is forced dismounted for the rest of her stock (with a new up special for recovery). It heals when she's not riding it, which represents Renewal. She could even have the
Triangle Attack as her Final Smash, although Stun works too (both works even better), and she would have access to it regardless of mount state. It'd be the only way to revive her pegasus without losing a stock.
For alts and colors, I imagine PoR/Princess Crimea Elincia, RD/Queen Elincia, PoR Geoffrey, RD Lucia, PoR Marcia, RD Tanith, PoR Bastian and RD Tibarn. There's another character I could imagine as a potential RD color, but he'd be a spoiler.
Lyon (
The Prince's Despair) from The Sacred Stones, represents all the dark magic in the series and its varying effects, such as the HP drain of Nosferatu (which jumped ship off of Robin for that reason), the resistance penetration of Luna, the far range Fenrir, and all sorts of other gimmicky weapons, as well as representing Magvel and the GBA games. If you guys want something more practical, his down smash could be based on Dark Spikes T from Three Houses, his grab could be based on Eclipse, and I don't imagine him as particularly gimmicky, although if his down special were actually his oft-forgotten ability to summon units, that could be interesting. While Naglfar is the obvious choice for a Final Smash, I'd prefer something more inspired by what Fomortiis does (either Demon Light or Ravager via the
Blood Tome, from Heroes), while Naglfar gets the illustrious position of Neutral Special.
For alts, I can see him as default, Knoll, Ewan, Riev, Nergal, Ephraim, Eirika, and Fomortiis.
Julia (the only reason she out-prioritized Micaiah is because Jugdral hadn't been done yet and Tellius had; for music, here's
The Final Holy War) of Genealogy of the Holy War rounds out the trinity of magic with light magic, being perhaps the frailest but also the most spectacular of the bunch, and also having her own set of staves (hers focus more on movement; Elincia might prefer status staves like Sleep while Julia has Rewarp and Entrap). Rewarp is a basic teleporting up special, while Entrap is both her down special and her grab (having similar grab mixups to Yoshi of all characters). She'd also smuggle in some white magic, faith magic, black magic and other tomes that fit the light magic theming: Saggitae (I envision a Forward Smash), Seraphim, Abraxas and Agnea's Arrow. For her and Lyon, I'd probably try to avoid giving them regalia tomes from other continents, though it's not a hard rule: it wouldn't make sense for Julia to have Ivaldi or Lyon to have Balberith, but it would be sick as hell. Her Final Smash being the
Book of Naga basically writes itself.
Alts: Default, Julius/Arvis, Seliph, Micaiah, and perhaps Deirdre as a full-on alternate character akin to Alph, with palettes for Caeda, Celica and Nanna.
If I need to sell you on Fire Emblem mages, here's some spell animations from the various titles:
GBA Era,
Three Houses, Radiant Dawn (
Dark Magic,
Regalia), FEH (
comparison, best NES/SNES/PoR/DS/3DS era references). Note that if any of you want to play these games some videos will have spoilers, especially the ones relating to Radiant Dawn.
I'd love to flesh out Elincia and Lyon a lot more, and to an extent Julia as well, but the main goal of this representation was to cut down on sword bloat (the only solo sword unit here is Marth; Elincia, the next closest, has an entirely different style due to staves and her pegasus), add more style diversity, and more era diversity (3DS was comically overrepped at 4 characters; even if Awakening was a huge success, only 3 of the Fire Emblem cast were from before 2010, and only Marth before 2000; under my proposed system, Marth and Julia represent the 90's, Lyon and Elincia the 2000's, and Robin and Byleth the 2010's, with the only console redundancy being Marth and Julia both being SNES and even then Marth is based more on the DS anyhow). (Debatably, Elincia,) Lyon and Julia are even non-protagonist fighters, Lyon being an outright antagonist.
This is pretty much the sequel to my Pokémon post. To be honest, that's FAR more likely to happen (Abilities in Smash) than this, but I do think showing Fire Emblem's greater potential is the way to go, if you want to help mend its reputation without straight up nuking the series off the roster.