I wouldn't mind a more complex weapons upgrade and/or custom loadout system like CoD, but I certainly don't want it to become crazy run and gun style combat. However, picking up the pace, even if just a little bit, would be welcome to me.
The reason Halo and CS have been, in a competitive sense, more viable is because they don't have 10000000009 different weapon set ups, the next always being more absurd than the last. I wouldn't mind a set up like they have in CS wherein you can chose a gun, rather than starting out with only the AR. But honestly I like the multiplayer aspect of halo as is. Really i don't want it to change. Having been someome who has been a part of the Esports community (albeit in world of warcraft, but hell i've been watching these competitive games now for 6 years live), the gameplay of CoD is really a negative for competitive gaming.
That doesn't mean that they shouldn't implement a new game mode that is decidedly more action packed. I'd be down for that.