I decided that instead of just listing individual ideas for Isaac, I would just post an entire moveset for him, and see what people think of my concept of a three-tiered charge character:
Isaac from Golden Sun
From Assist Trophy to Playable Character, Isaac's playstyle utilizes his swordsmanship as well as his Mastery over Earth and Plantlife. Most of his special attack deal with summoning the earthly elements, from earthquakes and boulders, to vines and thorns. Most of Isaac's moves at base are quick launching with a small radius and light damage, however all of his specials can be charged for greater damage, speed, and effect. This gives Isaac the chance to be suddenly switch fighting styles on a dime, from a low-damaging quickster to a slower powerhouse (at least in theory)
Melee:
Jab: AA: Sword slashes, two generic slashes followed by a third overhead slash, similar to Helm Splitter
FTilt: Glowing sword forward stab, based on Odyssey
UTilt: A full overhead slash, hitting most of what is in front of Isaac from overhead to floor, based on Helm Splitter
DTilt: Glowing sword stab aimed forward angeled toward floor, based on Ragnarok
FSmash: Isaac lunges forward with a sky to floor slash that created a short-travelling sword beam, based on Cutting Edge.
USmash: Punji, Isaac summons sharp-pointed bamboo from the ground and stabs upwards, they retract soon afterwards.
DSmash: Isaac summons several blades around his feet that stab upwards around his body, based on Sabre Dance.
NAir: Isaac balls his fist as purple energy glows and envelops him in a purple haze, damaged on contact, doesn't last long but lingers on any foe affected for a few second thereafter, based on Demon Night
FAir: Overhead slash from head to foot, based on aerial version of Helm Splitter
UAir: Spire, launches hand upwards conjuring a small spire of stone.
BAir: Lashes back with an energy whip, based on Whiplash
DAir: Sweeping plunge downwards, based on Death Plunge
Specials:
Special: Gaia->Mother Gaia->Grand Gaia: Chargable earth-based burst attack centered on self
USpecial: Rockfall->Rockslide->Avalanche: Chargable boulder that lifts Isaac into the air like a platform, charging creates a bigger and faster platform
SSpecial: Thorn->Briar->Nettle: Chargable vine grab, pulls self towards captures target into an explosion of thorny vines. Charging increases vine length (base vine doesn't have that more reach than a normal grab, whereas Nettle can grab from farther away). Can be used as recovery tether.
DSpecial: Quake->Earthquake->Quake Sphere: Chargable shockwave, damages and launches opponents up. Charge increases shockwave size, damage, and launch, fully charged includes a second, smaller shockwave. Ground version has a short animation, aerial version launches Isaac to the floor quickly and it enacts on contact. Aerial version can be cancelled before ground contact is made.
Grabs:
FGrab: Slashes forward to break hold then launches outward with his palm, sending a palm of white energy to knock opponent back, based on Move, but hand is smaller than current Brawl model.
DGrab: Isaac slams opponent to ground and then launches three quick but very small localized quakes, that launch opponent into the air at the end, based on Tremor
UGrab: Launches opponent into the air with barrage of whipping vines from ground, up-launch, based on Growth.
BGrab: Slashes back to break hold before Isaac punches forward, sending a balled fist of white energy to knock opponent back, based on Force
Dodge: Despite the fact it is a Psyenergy usually only used by Felix, was thinking of allowing Isaac to dodge by turning himself into a small sandstorm, using Sand, sort of like a short-range teleport and yet another nod to his earthy abilities.
Final Smash:
Planetary: Summoning the power of Gaia, Isaac causes any foe in front of him to be swallowed by the Earth and held as he summons a dragon of heavenly flame that quickly launches from the sky, hitting foes. (acts very similar to Ganondorf's Final Smash, with attacking point moving diagnoally instead of horizontally)