Do you even understand ARENA MULTIPLAYER? The point is that it is fast paced and the maps are small. You know it's been done before with Halo right?
Halo is still different from other games. Just because you can't get a vehicle straight away, although it's very easy, doesn't mean it's no longer unique.
What's the name of this Modern Warfare rip off map? I'd like to find out why you think it. Oh and a friendly tip, AR and SMG aren't the best, you just don't fight enemies with them with a precision weapon at close range.