In a JRPG like the SaGa series, there is a limited amount of people in your party. This makes it easier for people to fall into “roles”. However, in a SRPG like Fire Emblem there are easily 20 times the amount of playable characters. For such a concept like this to work, you would have to severely limit the amount of characters in your army.
My main idea centres around “character gets hit/uses weapon” and how that would affect stat gains… maybe the system would be too inefficient in this hypothetical SaGa-Like SRPG.
If it’s what you want to do maybe you could have something a bit like Alm’s friends in the early game of Shadows of Valentia, they start as a bunch of trainee/villagers that can quickly promote in many different classes. And with their different growth you are inclined to promote them into different classes
So you would start as a bunch of young villagers having to leave their home for one reason or another, and then find a reason for them to stay a little groups: maybe they are on an adventure to find a treasure, maybe they join a rebellion as a small squad that is sent on special missions, etc.
I mean weapon ranks in most games in the series basically already work like that.
You could probably make a system like this in LT, where a gauge fills up when you do certain actions or (more reminiscent of Pokemon EVs) kill certain enemies, and once it’s full you increase in that stat. Seems difficult to balance though as that would just encourage the player to turtle and draw out every engagement into as many actions that give points, so you’d probably need some kind of cap per map.
Maybe assign certain stats to certain weapons and actions. Moving increases speed. Steel weapons increase str. Stuff like that maybe? Killer edge increases skill.
You’d probably have to make them unlimited uses so you dont break them as your grinding for a stat