WI: Messenians win the First Messenian War?

The Spartans are famous for many things, and their society was unique among the Greek city-states for a number of reasons. As the entire reason it could maintain such a formidable army, it relied heavily on a force of hereditary slaves, known as helots. But the foundation for it all came in the First Messenian War, which up until then Sparta had been just another Greek city-state, albeit with some unique laws and a professional army, while significant elements of it are probably mythologized, it is likely something approximating this happened. What if it resulted in a Messenian victory? Could we see a reverse Sparta, with the Spartiates becoming helots? Would we see straight up conquest/extermination? Or could a "league" of some sorts form? How would it impact the Archaic and Classical eras? How are the political systems and development of Hellas affected? Is the response to the Achaemenid invasion different from OTL, if it is not butterflied away? What is the influence outside Hellas?
 
One possibility is that the Messenes destroy Sparta itself and the surviving Spartiates who escape slavery end up migrating to Taras. Taras might end up taking a role vaguely similar to Athens with the Delian League, dominating the other Greek colonies in Italy. It might unite the peninsula itself.
 
Well, we know nothing about how Messenia was like before the Spartan conquest, so it is basically all guesswork.
Also note that Sparta was the largest of the Greek Polis over double the size of Athens, so if we end up with a 'reverse Sparta', a single polis where the Spartiates are enslaved by the Messenians controlling the whole area, it is likely to be a mayor player regardless. Probably even more powerful if it doesn't kill a significant share of its population through the Cryptia or the agogue and does not need to always keep a part of army at home during war to prevent the slaves from rising up.
 
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