I'm in NZ, Born and Raised, I like the most recently posted Oceania, I would have placed more emphasis on the southern cross as Oceania to me is majorly Australia+NZ (Population) as Japan etc. is generally considered Asian. But that'll be because I'm in the region, skewed viewpoint.
Peace symbol is a combination of N and D in Sempahore. Nuclear Disarmament, grew to be anti-war in general, hence peace.
The more you know...
I would personally try (And may end up trying, although any 2d art I do will just be concept, to flesh out my ideas for better artists to consider) to incorporate a shield into the logo, as part of the phalanx thing (A major part of the greek phalanx was the shield) and an overall feeling of defending the earth, spear is good as it gives the feeling of agressive defense (Offense) without the nastiness that a gun says, as well as the whole phalanx thing.
Not too fond of the moon = outside idea, Phalanx was put in place to defend from aliens, and it was always assumed that they were outer solar system at the closest (I'm sure you all know the spoilers) so moon probably wouldn't represent outside suitably. Maybe look at something traditional for a defense force and say that they kept the 1950's phalanx flag or dont show the old flag and only reference it.
I guess if art was provided for 50's and modern Phalanx and they worked in that context, use both in the game.
And yes I am aware I sound pretentious, I like to be thorough so that someone can get something from what I say. It's worth it if it helps improvement.