I kinda think this is going in the wrong direction. I agree with rungok, it would be easier to create a subsystem based on aura and dust and then create two or three classes based on that system and then use archetypes to mold closer to each character. Maybe some archetypes to normal classes too, Blake could easily be a Slayer or Ninja using an Aura archetype and Yang could be a Brawler or Monk archetype.
So what do we know about Aura?
It passively increases your strenght and speed while it's on. Either have this passives as part of the class features or maybe something like spending a point activates aua for a minute and then you get the passives during this minute.
It gives you a defensive aura, but any damage you take drains your aura. Having Aura active gives some temp HP but if those temp HP are consumed you start losing Aura points, maybe?
It fuels your semblance, which can be anything from healing to superspeed, to magic. The aura based classes could have a list of normal semblances maybe with some advice for the DM on how to create other semblances. Archetypes would be basically having that class as a semblance, so an aura using barbarian is actually someone with a semblance of Rage (Yang would then be an Aura Barbarian with elemental powers and using an unarmed style, maybe multiclassing with Aura Brawler or the Aura Warrior class), the archetype of ninja that replaces Ki with Aura is the semblance of Stealth or the semblance of Shadows (Blake) and the archetype of Magus that uses Aura togheter with Arcane Pool has the semblance of Magic (Glynda) (Maybe a fullcaster? not sure) and the paladin archetype has a semblance of Healing or of Good (Jaun, at least according to fanon).
Here's a rough draft:
Aura (Su): At level 1 you gain a pool of aura points equal to your constitution modifier + your level. As a ??? action you can spend an aura point to activate your aura granting +2 morale bonus to strenght and dexterity and 5 temporary HP per level. Your aura lasts for one minute or until you lose all you temporary HP. If your aura is deactivated through damage you can spend an immediate action to reactivate it. You need your aura active to use your semblance.
Greater Aura: At level 10 the bonuses to strenght and dexterity from having an active Aura increase to +4 and the aura lasts for ten minutes unless you lose all your temp HP.
Infinite Aura: At level 20 your Aura is always active unless you lose your temporary HP. You still have to spend an aura point to restart your aura in that case. Your bonuses to strenght and dexterity increse to +6 while the Aura is active.
Semblance (Su): At first level you select your semblance. A semblance works only while your aura is active. Spending an aura point to use a semblance ability is a free action unless stated otherwise.
Semblance of Speed: You gain a +10 feet increase to your base speed while your aura is active. This increases by +10 feet at 8th and 16th level. You can spend an aura point to double your speed for one round. At 4th level you can spend an aura point to make a turn as part of a charge. At 8th level you can spend an aura point to gain the Light Steps class feature like a ninja of your level for as long as your aura is active. While using this ability you can also run on walls and ceilings but you still must end each turn in a vertical surface capable of holding your weight. At 12th level you can spend an aura point to gain the benefits of Haste or Air Walk as if cast by a wizard of your level. This spell is dispelled if your Aura is deactivated. At 16th level ???. At 20 level ???.
Aura Stunt (Su): At 2nd level you learn to use your aura to subtly bend the laws of reality in favor of awesomess and style. As a free action you can spend an aura point to add 1d6 to the result a d20 roll. This can be a skill check, ability check, attack roll or a saving throw. You can only do this once per roll. When using an aura stunt you must describe your action in a properly awesome, badass or stylish way.