I think this is a great explanation of what is to come with the whole "perks", "armor abilities", and "loadouts" reveal:
http://www.nowgamer.com/features/1270434/halo_4_multiplayer_plot_gameplay_round_up.html
"Halo 4s multiplayer has custom classes
343 Industries explained to us that Halo 4s multiplayer modes will feature custom class and load-out creation, but OConnor stressed that Halo 4s multiplayer will not be a Call of Duty clone.
OConnor also explained that players will earn gameplay enhancements through progression, hinting at rewards for levelling up to further bolster your multiplayer character. However, the studio was unable to elaborate on this further."
I'm guessing you'll be able to pick from a limited selection of starting weapons (BR/AR/DMR) and maybe even secondary weapons (Pistol/SMG) for your classes.
That along with your armor customization will affect your gameplay experience.
Hopefully we find out more in this week's bulletin.
Fuck That.
Give me classic Halo done right and nothing else please.