OK, So hear me out. I'm thinking that for one of the most popular game modes in World at War, which without a doubt is "WAR" you bring it back with maps designed specifically for it!
These maps will be HUGE! With at least 30 people playing (15 on each side), you can add Humvess or jeeps to this game mode to create mobility. Also, you might want to add pilot able helicopters... You know, two in the chopper, but easy to shoot down....
I think this will be a hugely successful game mode as you will always find the action somewhere with 30 people playing.
Also, bring back customisable Kill-streaks... I found this highly enjoyable (but no game-ending kill-streaks), I liked coming into each game, knowing that I would have to work for a predator or a harrier and not just a lousy UAV (Don't flame me).
Juggernaut- no real opinion, it's fine, just keep stopping power if you're going to re-introduce it!
Things to tone down- Noob Tube- Have them, if you want, but please don't make them as easy to obtain as MW2, maybe lose Scavenger, bring back Bandolier and lose One Man Army... and Danger Close.
Please bring new, interesting Kill-streaks... perhaps Napalm... or (just a random idea) A group of mercenaries which supply covering fire for a minute or so.... something that will make us play for longer, keep playing and never, ever stop.
This is what I think will make Black Ops the greatest Call of Duty...in 2010