: The rationales you described go alongside the human sandbox, though. Halo CE
: is the only game where Bungie didn't attempt to provide alien analogues to
: the human sandbox, and that was largely by necessity (since starting with
: Halo 2 you'd be playing in places where you couldn't presume to have
: access to human weaponry.)

And because of that, Halo 2 and 3/ODST have the weakest gunplay out of the Halo games. Halo:CE was best for not having direct counterparts, and Reach went the route of making the analogues play as differently from each other as possible. Some of them, like the grenade launcher and concussion rifle or the spartan laser and the plasma launcher, share only broad similarities.

And even in Halo 2, there was more difference between the battle rifle and the carbine than there is between the battle rifle, DMR, carbine, and light rifle.