That wouldnt be terribly hard.
Something akin to an elemental duelist, where you apply certain elemental debuffs to proc other effects when using different abilities.
You could even make it a status based gamplay where you apply dots/debuffs based on what elements combine.
Fire/Ice/Lightning/Earth
Fire+ice = water
Fire+Light = Explosive
Fire+Earth = Lava
Ice+Earth = Frozen
Ice+Lightning = ???
Lightning+Earth = ???
Each combination could apply different DoT or Status effects that help your party.
There we go, a job that doesn't have a gauge and plays extremely unique compared to anything else in the game.