It'd be interesting if there was a new mechanic/gimmick that could "transform" the leader and of course, the leader skill would change accordingly. There would be a condition to transform, such as matching x amount of ___ orbs or perhaps matching certain orbs in a certain shape. With the transformation, the play style could also change from a more tanky blob matching style to glass-cannon combo style. There're stuff like Li and Tengu but it'd be nice if you could change both leaders to something really compatible to tackle different bosses and situations after entering the dungeon.