@cabalxxvi: The concept of your character is solid. Though I do have a quick note for you and an issue.
The note being that you mention him fighting for/serving the king of Sparta. During the time of the Roman Republic there still were Spartan warriors trained to fight in a Greek Phalanx and raised 'the Spartan way.' However by this point in history Sparta (and Greece itself for that matter) was no longer independent as Greece was already conquered by Rome. Though the Spartans were still allowed to continue their way of life and were given a decent amount of freedom to handle their own internal affairs so long as they paid their taxes to Rome. So while there would still be a 'King of Sparta' he would have been more akin to a mayor with regards to his power/authority. And there wouldn't have been any battles he and his Spartans would have been in, other than serving as Roman Auxiliaries. So while it doesn't necessitate a change in your character's bio it is just something to keep in mind when/if he talks about his personal history.
The issue I have is that you have your character being of Gallic origin, but the Spartans were actually very xenophobic. Especially when it came to providing a Spartan education to males. The only boys who would have been allowed to undertake such training would have been those born to Spartan citizens, the sons of helots deemed to be deserving, (second class citizens within Sparta who were the descendents of other Greeks the Spartans had conquered/enslaved) and the sons of foreign dignitaries who sent their sons to apprentice in such a lifestyle(which was very rare). This is actually the only aspect of your character that would need to be changed. Other than that, and pending you posting your stats, he looks good.
With regards to having him be house champion I know Holmes expressed interest in the role previously. I'll shoot him a PM to see if he still has interest in it. If not then I'm fine with whoever wants to fill the role.