I think it would be nice if each recruitable champion has a unique trait that goes along with their backstory. Currently there isn't much that differeniates them. They either have magic skills or they don't. They might start with a path of the x but that is about it. These unique traits don't have to be just a one time starting trait either. Maybe they open up a level 2 or 3 version as you level up or maybe a new trait altogether. Without something like this the Champions are all pretty generic.
Some examples: (I don't claim to be original with names lol)
Shadow the Assassin - Starts with a "Poison Attack" ability. All melee attacks add poison status that does 2 damage a turn. It can be upgraded to Poison Attack 2, 3, etc each one doing more damage per turn.
Vivi the Black Mage - Starts with the "Dark Attunement" ability. Dark spells cast by Vivi have an extra shard of power.
Fung Shu the Monk - Starts with "Inner Peace" ability. Regens 1 HP a turn in battle. Can be upgraded to Inner Peace 2, 3, etc
Whoman the Barbarian - Starts with "Tough Guy" ability. Flat out +4 to strength.
Barbosa the Pirate - Starts with "Treasure Hunter" ability. Gains more gold after battles.
Rolan the Knight - Starts with "Mounted Combat" ability. Gains an extra +1 to moves and +2 to initiative when on a mount.
Frodo the Meek - Starts with "Quick Escape" ability. Gains +5 to dodge when under 25% hp.
Moses the Sage - Starts with "Arcane Adept" ability. Tactical spells have an additional 25% reduction to cost.
Ronin the Sword Master - Starts with "Fencer" ability. Attack is increased by 5 when weilding a sword. Can be upgraded to Fender 2, 3, etc
Norman the Necromancer - Starts with "Raise Undead" ability. Once per battle can raise a skeleton to fight for him. Can be upgraded so maybe level 2 is a zombie, 3 is a lich, 4 is a zombie, and 5 is a bone dragon.
Draco the Dragonborn - Starts with "Fire Breath" ability. Can breath flames once per battle that does 7-12 fire damage to foes up to 3 tiles in front of him. Can be upgraded to do more damage or allow more uses.
Jester the Acrobat - Starts with "Tumbler" ability. Has a small change to evade a melee attack and move to an adjacent square if one is free.
Rori the Serpent Hunter - Starts with "Serpent Hunter" ability. Gets +50% bonus to damage vs nagas, serpents, and 20% bonus against dragons.
etc . . .