After playing Mass effect 3 I think it would be pretty awesome, not only would you customize your Spartans look, you would customize his weapons, class, and perks/unlocks.
Also calling in AI buddies Via air drop and things along those lines would be great.
I think if they don’t do something like this they’re missing an opportunity.
Heavy Spartan, Sniper, Rifleman, Assault, and Stealth style. Seems like it would work to me, and Elites could get a similar thing depending upon their role in the game.