I think that Halo 4 pretty much hit the boundary for the maximum quantity of armor sets that can be included while still having them all be (mostly) distinct from one another.

Armor design is definitely my biggest gripe with 343i's art direction. They don't take nearly enough time to clean up and focus their designs before building them as finalized assets. The visually noisy designs that they put out look neat in motion, but just don't have the kind of staying power that comes from a strongly defined silhouette and conservative application of fine detail.

It also doesn't help that 343i seems to pretty frequently farm out building MP armors to contractors, resulting in the in-game assets being of inconsistent/variable quality.