Initially the game was called Emblem Saga; the name was changed to Tear Ring Saga because of "various circumstances", but fans speculated that it was to avoid the obvious lawsuit from Nintendo. Despite the name change, Nintendo filed various lawsuits against Tirnanog and the publisher, Enterbrain. Enterbrain was found guilty and fined for breaking the Unfair Competition Law, but not for copyright infringement.
Manaketes were going to appear. Given that Intelligent Systems has trademarked the name "Mamkute", they were replaced with the nigh identical Emiyu.
Runan was going to have blue hair, like almost every other Fire Emblem lead.
It would have been possible to "choose" the main characters by choosing who leads the armies.
The type of battles the player has the armies fight will determine what the units within specialize in. (For example, arena grinding would eventually make the army good in the arena, but bad in group combat)
Growth rates were to be replaced with "growth curves", growth rates that change as the unit levels up.
The game was originally to use an isometric view, as in Final Fantasy Tactics; Berwick Saga would later use a hexagonal variant of an isometric map.
Nintendo losing the copyright infringement lawsuit set a precedent that stated it was OK for creators to release derivative products based on franchises they once helmeted without having to worry about possible legal actions by the current owners of said franchises. See Bungie leaving Microsoft and Halo behind in order to release the similar Destiny, Keiji Inafune leaving Capcom and Mega Man in order to create the similar Mighty No. 9 and Koji Igarashi creating a CastlevaniaSpiritual Sequel with Bloodstained: Ritual of the Night after leaving Konami.
Due to the legal mess the game caused, there's still some bad blood between Shouzou Kaga and Nintendo, to the point that Kaga got pretty much unpersoned by the Big N. Case in point: Kaga wasn't even mentioned in the The Making of Fire Emblem 25th Anniversary book, despite being the mastermind behind the entire franchise. This is the equivalent of writing a book that details the entire history of Star Wars in such a way that omits mentioning anything about George Lucas.