Huh, I just learned that Arle Nadja came from a JRPG franchise before she was in Puyo Puyo...
Yep! Arle was the protagonist of Madou Monogatari, a series of dungeon crawler JRPGs that started in 1989. The Puyo Puyo series actually started as a spin-off of Madou Monogatari. I believe the last MM game before Puyo Puyo completely took over was for the Sega Saturn
(and it looks pretty darn cool).
In the Puyo games, when Arle makes a chain, you'll notice that she performs
(or shouts out) spells such as Fire, Ice Storm, Diacute, Bayoen, and more. Most of the spells she uses in the Puyo games originated from the Madou series
(I think the only one that didn't is Heaven Ray, which apparently came from "Waku Waku Puyo Puyo Dungeon", which I'm not too familiar with). Arle's a mage with access to tons of spells, which is why when people claim she doesn't have "moveset potential", I just assume they don't know much about the character.
Even if you were to limit her to only the spells that appeared in the Puyo games, she'd still have access to:
Fire/Fireball -
Flame-based magic that can be used for offense. In most appearances, it shoots out fireballs.
Ice Storm -
Ice-based magic that serves as the ice counterpart to Fireball. Often depicted as a snowflake attack.
Thunder -
Electricity-based magic that serves as the electric counterpart to Fireball & Ice Storm. Depicted as a bolt of lightning.
Heaven Ray -
Holy-based magic that causes Arle to be lifted in or by a beam of magic.
Jugem/Judgement -
Non-elemental attack magic that is extremely powerful.
Brain Dumbed/Mind Blast -
Magic that can induce stupidity. Takes many forms, and can either lower attack power, or even prevent the enemy from doing anything.
Diacute -
Magic that increases the power of any spells used after it. It also usually causes Arle to stutter the name of the spell.
Revia -
Magic that retaliates any damage Arle takes to whomever it was that attacked her.
Bayoen -
Arle's most legendary move, and her signature ability. It rends the hearts of those nearby, allowing her to paralyze or otherwise distract them with flowers. Occasionally, it takes a more offensive form, being a collection of random objects such as planets and stars or lots of Puyo, and can even be used as a burst move.
(The descriptions were taken from the wiki for the sake of convenience.)
And there's more if we include "Waku Waku Puyo Puyo Dungeon"
(since it does have Puyo Puyo in the title). Most notably Speed Down
(a spell that slows a target down) and Speed Up
(a spell that speeds Arle up), which I can see working rather well in Smash. And this is all without getting into whatever crazy Puyo-based gimmick she'd more than likely have. She really has the potential to be one of the most interesting fighters in Smash.
If anyone's interested in seeing her full list of spells, it's all on this page here:
https://puyonexus.com/wiki/Arle_Nadja.
If it isn't already obvious, I really want Arle in Smash. Given that Puyo Puyo is Sega's second biggest franchise right now, I think there's a chance it could happen. Here's hoping, I guess.
(I spent far too long writing this post, lol.)