I would define Arcane as "bringing Order to Chaos."So it would be a blending of Astral/Divine and Material/Elemental, representing the Nexus of these cosmic forces.The only thing it would be missing is an Elemental power source I blame the 'Arcane' power source for being way too vague. That's probably an area I would break with D&D tradition if I was making a new game: define and limit 'magic' so other power sources can better stand on their own and relate better to the rest of the cosmology.
For an Elemental Class, I had this idea for years now of a sort of close combat Controller/Defender that channeled the Elemental Chaos through their equipment, transmuting their heavy armor and other gear into fonts of elemental power. Imagine this heavy armoured character who suddenly gets engulfed in flame, or his armor becomes blades whirling around him or sprouts spikes of sharp rocks...
I wonder if it would have made sense to connect the Sorcerer to the Elemental Chaos?