I think that 343i tried to compensate for the weapon same-ness by decreasing the spare ammunition capacity and cleaning up the maps more often. This way, you were forced to hunt down one of the many, many ammunition caches or use the gun from the last thing you killed.
: I think for the future, 343 should eliminate weapon duplication, or else
: allow an entire arsenal to be carried like in 90s FPS games.
OK, so what if Halo had a hyperspace arsenal? We'd still have to cut out the duplicates, because nobody wants to cycle through three mechanically identical automatics on their way to the rocket launcher.
What if we go through a whole Halo game with only a single transforming Forerunner weapon? It could take on several different 'aspects' for close quarters, mid-range, and long range combat, and several more for the niche weapons. Canonically, it would be a weapon designed for front-lines usage, where individual soldiers would have Ancilla to help them react to the shifting battlefield.
-Close range: Not a shotgun. Anything BUT a shotgun. I'd like something that throws enemies around with powerful gravity fields and does damage through tidal forces.
-Medium Range: I'd retool the Railgun from Halo 4, slightly. Maybe make it charge faster.
Alternatively, the medium-range aspect would launch volleys of needles that shred and sterilize a target, as was seen with the Sentinel Enforcer.
-Long Range: Sentinel beam, with a scope.
-Niche One: Anti-aircraft. Yanks airborne enemies out of the sky with the force of hundreds of gravities. Bonus points for dropping it on enemy troopers.
-Niche Two: Incineration cannon. Lock onto one enemy and vaporize it. Nearby enemies are hit by the blast wave and have to deal with being covered in the ashes of their best friend.
-Niche Three: Something with cluster munitions. Call it a MIRV, and I'll kill a kitten.
Another feature we can add to improve the combat is rechargeable abilities that can be accessed independently of what weapon is wielded. For example, one ability could grant shields to an ally or lock down an enemy, and another ability could drain enemy shields and overheat weapons.
So, we'd be recreating the original Mass Effect combat system, with better primary weapons. It's an idea whose time has finally come.