@Calane about DQ, but I can try with the knowledge I have. It's been a while since I played the games, so bear with me.
Erdrick have the class of "Hero" unlike a lot of his party member, he cannot Class-shift. But why would he? Have have the largest arsenal at his disposal.
While Erdrick's main signatures weapons are the Sword and Shield, he also can use Club/Spears/Axes/Whip/Boomerangs (Please be this I need Eight as an Alt)
Which mean that for his aerials, or special, just like the Belmonts, he could use others weapons. His Dash attack can be a Shield bash, he could have a back air that disjoint by pulling the whip, his down air could be him going full Dragoon jump with the spears going downard.
His smash Attacks can change weapons depending on the direction. Who knows.
And that's just exemples I can think on the spot, there much more possible.
As for his magic side, Erdrick have been associated with the "Zap" spells, being the thunder element. However they're never really seen used like Robin by tome or whatever, as Erdrick
Literally summon thunders from the sky so kinda like Pikachu down's B.
His Neutral B can be having a line of tiny cloud appearing on stage, and being able to push B again to summon the thunder to strike oppenent and have stage control when he need it.
He could use "Sizzle" to summon collums of Flames that can be a weak AoE attack to keep distance when in dangers
He could use "Poof" or "Zoom" as his recovery, or summon a slime to jump on it if you want to be imaginative
Erdrick can be 100% unique and that post only needed 2 minutes of thinking. So imagine what Sakurai and his team can do with months of works.