Dream Class was an ability Leonel had created back when he felt that he had too many paths to follow. He split his skills into archetypes to raise his efficiency in battle.
He had created a Sniper Archer and Explosive Archer Class, a Strong Spearman and Flexible Spearman Class, a Mixed Fighter and Speed Fighter Class… so on and so forth. Then, he assigned them all stats.
The goal was meant to allow him to track his progress and be more ruthlessly efficient in battle. Because he was such a calculative fighter, it took a toll on his mind to eliminate all the abilities he shouldn't use and hone in on the ones he should.
This Dream Class ability was meant to cut all of that out by choosing the archetype that would best counter an opponent in a situation.
Essentially, it was practically like swapping characters mid-game.