Can you really say "what exactly is historical"? We're dealing with several hundred years of pretty significant changes--political, social, economic and presumably military. Historically, the elite of the equals in 272 probably looked different from the elites in 222, and so on. Even within the soldiers in 272, some of the soldiers probably had fancier cuirasses than others. And unless you know of some Hellenistic period greaves or tomb paintings or reliefs or cuirasses from Sparta, then its all pretty speculative anyway.

And may I suggest being willing to make a small stretch by including "beauty" as a factor in discerning reasonability/accuracy, especially in a speculative case like this one.