The changes involve a bit of alternate history.....essentially, the Spartan agoge would represent the equivalent of the Hellenic world's premier military academy with the same rigorous focus on athletics as it's historical counterpart, but with leadership, tactics and such thrown in for good measure. So, the trait change would need to reflect it, but not too much (maybe a command star or something small like that).

Ideally, in my game I'd avoid using the hellenic spearmen at all or in very small numbers and relying entirely on phalanxes (something I usually avoid, as personally I find the other Seleucid units far better....) until a character comes along who excelled in the agoge, who represents the same kind of reformer as for the Romans, and who manages to win enough battles with these new troops to prove their worth. At this point, I'd start raising the heavier variants.