Wouldn't be surprised if there was some legal stuff surrounding the Security helmet's design since it's just the Marathon Security Officer's helmet and once Bungie took off they didn't use it anymore. See also: Marathon logo in CEA, possibly some emblems going from 3 to Reach to 4.
Also, that's a picture of Mark VI, which is totally in the game. It's the best looking helmet the game has. Wish H4 had Mark V, I'd use it in a heartbeat. Can't stand the abundance of helmets in H4 that just look like crummy faces trying to be badass. War Master looks like a Spawn wannabe. Defender looks like a crying clown. Half the H4 armors have visors that are basically just eyeballs.
On the topic of armor, I wish there was a way to toggle the undersuit to be fully black. There's a real contrast problem with the H4 armor sets, and everything just kind of blends together, especially on the cards and in the armory. Maybe it wouldn't work because of the armor pieces being more separated than before, I dunno. I'm no artist.