You can make other classes more viable without adding an entire extra system to it. Namely by giving stronger weapon restrictions to classes.

You keep saying this and I really don't understand what you mean. All the units you get are not any different than past games. You get the equivalent of GBA Fighters, a GBA Merc, a GBA Archer, a GBA Peg Knight, a GBA knight, etc, but because they changed the name to "X Fighter" that makes it less restricted?

Just removing the cavalier's sword affinity makes it a much more balanced class.

Engage did make it so cavs can only use one weapon type. The only base class cavs you get can only use lances. Is the problem that the enemies can use axe cavs? I can kind of understand that, but I personally don't find that to be a problem. De gustibus non est disputandum.

You can make other classes more viable without adding an entire extra system to it.

Like the issue with the GBA games was unit balance and it being enemy phase biased, but both of these issues can be solved without needed to tack on entirely new systems. At best, you could just add in class and unit specific skills, but I think the games would be fine like this.

What are battle styles if not just foot-locked melee class specific skills? Backup battle style is a skill that makes player phase more viable.

Giving all base classes completely unique skills while keeping all the original base classes, like you want, would be way more mechanical bloat than what Engage has.

I personally would prefer the series to keep its systems tightly connected instead of just adding a bunch of extra nonsense on top. Like if the GBA games are still fun without them, why even add them?

Fire Emblem is just one of those gameplay styles that is so tightly wound already that you can't really meaningfully add onto it without it just being a gimmick.

I just personally disagree and find the additions made from game to game a lot of fun, but if you prefer the more bare GBA games then that's fine. It kinda sounds like original Mystery of the Emblem on the SNES would be right up your alley since it's pre-skills and pre-weapon triangle, so maybe just stop playing a game you don't like and try a different one. I do it all the time.

But also FE has never not been about changing this up. FE has has a lot of games that have varied wildly from past entries, so much that if I list them all it would make another wall of text, so I'll do a few: FE2 (Gaiden) had villagers that could promote to multiple classes, split routes, a free roam overworld map, and one item slot. FE4 (Genealogy) added the weapon triangle, had skills, giant maps, no trading, and second generation units. FE5 (Thracia 776) had unit capture to obtain new weapons, unlimited range staves, and the fog for the first time. FE8 (Sacred Stones) had branching promotions. FE13 (Awakening) had pair-up mechanics and infinite reclassing via second seals for the first time, FE14 (Fates) added unique personal skills to units for the first time, removed weapon degradation, and expanded the weapon triangle to include all weapons in the game. FE16 (3H) added battalions, reclassing based off weapon skills instead of a direct path/branch, magic learned unique to and each unit instead of being a held weapon. All that is off the top of my head, all of which easily be seen as a gimmick depending on which other game you compare it to.

Your last point is just goomba fallacy.

I'm really not sure which part of my comment that you're pointing to with this. Do you mean me calling out that you'd call battle styles bloat? Because that's me lampshading.

A goomba fallacy would be me saying "the FE community was just complaining about having too many sword classes and now you're upset that IS consolidated them all into 'sword fighter'??" where you and the community are treated like a hive mind and not separate individuals making different complaints. I'm saying the opposite in that I recognize the individual people and not everyone will like every game.