Would it have had more dramatic potential, to have Khan
On the Khan part...no. There's no emotional connection between KNS and the TNG crew at all. Once KNS was revived ("Space Seed
"), Kirk became his eternal opposite--an enemy/competitor for all time. Kirk's particular thought process / heroic determination to not bow down to anyone was the perfect answer to a person bred to think he was the ultimate human. That outright challenge made the Kirk/Khan conflict one of filmed sci-fi's best, with TWOK being the natural conclusion to Khan's story.