What do abilities/classes do in this game, really?

[Imdesperate]

So I know it might seem like a stupid answer, but what I really mean is the ability you get when you master a class. I found out that its class specific. For example, I leveled Petra up to max out Theif, but when I change her into a mercenary, her steal ability is gone. So what's the point of maxing out your class? What if I get too many abilities and i wanna trade one out for a new one? Is there a way to keep your abilities, of so how? I know that there are leveling stats the differ based on what class you're in, bit is that it? What's the benefit of mastering out a class? Sorry if this is confusing, it's just that I've never been confused with a class system before xD

 

[Vorena]

Abilities earned through leveling up weapon level or a mastered class stay with you regardless of class. You need to go to press X, then Inventory -> Abilities to swap out the 5 ability slots you earned for any class.

There are class abilities which are only mapped to the class. Most of the mastered abilities later on are really the ones you get at like S or S+ rank. For example, a Swordmaster requires A rank swords, but class provides you a free Swordfaire and Sword Crit bonuses so you might never need to get S/S+ rank provided you never swap from that class. 

Finally, every unit has its own unique ability that will be there regardless of class and can never be swapped out.

Edited August 13, 2019 by Vorena

[wissenschaft]

Classes in this game don't actually effect stat growths that much. The real reason to level a class is to max it so you can gain the mastery skill. Just google Three houses classes and you'll find lists of the classes in the game and the mastery skill they unlock. There are a lot of powerful skills to grab. For example, maxing thief allows a character to always have steal equipped no matter what class they are.

Edited August 13, 2019 by wissenschaft