After the Spartan victory over Athens in the Peloponnesian War, Sparta stood as the dominant power in the Greek world. One man in particular, Lysander, was in large part responsible for the victory, and had gained a great deal of power in Sparta. Lysander was half-Spartan, with a Spartan father and non-Spartan mother. He advocated the creation of a true Spartan empire, and a political revolution in Spartan that would allow him to rule that empire despite his half-breed status. Sparta's big problem was a lack of manpower: by this point there were only about 3500 Spartiate warriors. Meanwhile, there were a large number of people living in Sparta who were half-breeds similar to Lysander, or who were former Spartiate families that were now barred from full citizenship due to lack of land. With their limited numbers the Spartans didn't have much room for error, and ended up fumbling their chance for a lasting Greek hegemony.
What if Lysander had managed to push through a radical change to the Spartan system: keeping the intense warrior-producing Spartan lifestyle, but allowing significantly more people to enter the Spartiate warrior class, including half-breeds and the relatively poor. The Spartans use these improved numbers to expand their system, putting the rest of Greece in the position of the Spartan helots: the economically productive but militarily weak masses toiling away on behalf of the martial elite.
Plausible? Maybe not. But I did enjoy the full circle nature of basing an alternate Spartan history on the Draka, who were in turn based on the Spartans.