I really hope they just leave the H4 customization stuff (the original stuff, that is) all unlocked for everyone. A lot of us put a good amount of time into the grind with the original release to unlock everything. I didn't have much fun grinding through to get all the Reach unlocks in MCC because I'd already unlocked almost everything through countless hours of playing vanilla Reach, and I'd personally feel the same way about Halo 4.
That said, any new customization items like new visor colors (I wouldn't be too upset if even the existing visor colors and armor skins get locked behind SP), any potentially never before released pieces, etc are all totally fair game to add to the Season unlock system, IMO. Nobody's had to grind for that stuff before, so the problem of people having to grind twice for them is eliminated. I have to qualify all of this by saying that unlike a lot of other veteran players, I'm honestly not bothered by "newbies," having access to the entire armory off the top. I'd rather everyone have access to everything than having to grind pointlessly again to unlock a ton of stuff I already did years ago.
The high tier armor has never really meant anything regarding skill, with a few notable exceptions, and I've always thought the elitist attitude some players use when looking at beggining/early unlock cosmetics from games like Reach and 4 as "trash," just because they'd never dream of using anything less than the highest-status unlocks they have. Just a little pet peeve of mine, and it's certainly not everyone who reps high-tier armor I'm referring to, but I think we've all experienced examples of what I'm saying.
Overall, my biggest hopes for additions to the H4 customization is a toggle for all black or traditional colored undersuits (this would be amazing!) and additional visor colors.