Not possible, the demographics just don't allow it
You can't really compare Sparta to Rome. Sparta was, for starters, not expansionistic. They were loathe to send their armies beyond the Peloponnese, and for good reason-their entire system rested on keeping down helots that vastly outnumbered them and could revolt at any moment. Furthermore, Rome could survive defeats and bounce back, and frequently won through their ability to raise army after army, rather than any innate battlefield superiority. Sparta, on the other hand, was perpetually one major defeat away from ruin, and when that defeat came, Spartan power was shattered forever.
If you want Sparta to be an empire, it cannot be Sparta. They would have to ditch the helot system, and as such they would have to completely ditch their whole social system, which was completely reliant on having helots so Spartan men could spend their life as professional soldiers. And even then you would still run into the problem of there is no reason to expect Sparta to ever get the population size necessary to dominate Greece in a world where Spartan soldiers aren't really any more special than their counterparts.
That's not really accurate either. North Koreas main military strength is sheer numbers. Sparta has better quality soldiers, but at the expense of virtually everything else..So basically Sparta was the ancient worlds equivalent of OTL North Korea?
Think that PoD could have created a Sparta that could have potentially garnered enough power to retain some degree of independence well into the late republic?Yep i would go with Cleo he predated Nabis in the reforms. This would give you more time to build up a better power base, population, and alliances (Rome). Nabis carried on the reforms of Cleo but was in a diminished capacity at that time. If Cleo had been successful you would have had the rest of the Punic wars to build your base, be an ally of Rome vs Philip V to gain a stronger footing vs the rest of the world
Think that PoD could have created a Sparta that could have potentially garnered enough power to retain some degree of independence well into the late republic?
Cleomenes could have done something great for Hellas but we ran into the ''Not Sparta anymore'' caviat once more. The day's of the Polis where long gone when he came around and to keep going he would have had to truly brought on boards other cities into a greater league with him as the hegemon. Such league would inevitably cesse to be ''Spartan'' in due time and would become more of an helenic melting pot.
Bassically, Sparta would have been more a tool used by Cleomenes to create whatever he would create then the real beneficiary of his deeds.
By that logic the Roman Empire went from "Roman" to "Latin" to "Italic". Sparta leading, and being the centre of authority would surely make it Spartan no?
Not really. The Roman government was controlled by Romans. Affairs of state we're conducted in Rome, elections were held in Rome, the Senate of Roman citizens convened in Rome, etc. A better comparison to the distinction between Roman and Latin would be maybe the distinction between Spartan and Lakonians.By that logic the Roman Empire went from "Roman" to "Latin" to "Italic". Sparta leading, and being the centre of authority would surely make it Spartan no?
At the very least a "Spartan Kingdom" rather than "Spartan Polis"
Sparta had been a Roman Ally durring the time period in question and had helped the Romans penetrate Greece. I don't think anyone would object to the statement that Rome's weaker allies quickly became client states.I'm not sure "Stronger Sparta" and "Subservient to the Republic" work together.
Although, it'd be amazing to have Sparta keep the Romans out of Greece and be able to have two "Defenders of Greece" style titles.