Since we did not get Sorcerer as most people thought with Tabaxi, and as a cheap development idea, why don't you just make Iconic Dragonborns. Make their class Sorcerer. Give them Metallic dragon skins instead of the Chromatic and change a few enhancements, bam you are done. Easy, low effort Iconic ready made.
BTW, it always bugged me that you went chromatic, i.e. evil dragons, instead of metallic.