I'm in favour of stat tracking similar to multiplayer. Total kills, revives, headshots, points etc. Obviously challenges, rankings, emblems etc all in there as well.
I got to 68 on ascension last night with my buddie, when we play together we always cover a range of topics as we chat to keep our minds from going numb from the endless rape trains we have to build up.
One thing we talked about last night is as we noticed i had 2600 kills with no downs on rd 54 - killstreak rewards in zombies. The ability to call in / activate killstreak rewards for killing a certain number of zombies without been downed. Could also add in team killstreak rewards for the whole team reaching a certain amount of kills without any downs.
Nothing terribly overpowered by slaughtering waves of zombies but some (possibly bad) examples might be
100 kills no downs - call in a napalm strike that covers an area roughly the size of the kino stage killing all in it's drop zone instantly and leaves napalm on the ground for 10 seconds which will hurt / kill anything that runs through the area. - Roughly about 20-30 kills
200 kills no downs - air drop a placeable sentry gun that will last for 1 minute which has the power of a death machine. get it to hold a window or an alleyway or place it in a corner to spray at your rape train. 30-40 kills
500 kills no downs - call in an attack helicopter that will circle the map for 1 round killing any outdoor zombies at a rate of about 2 every 10 seconds so on rd 30 an attack helicopter might get you about 40-60 kills.
1000 kills no downs - Call in a wave of 15 attack dogs that will aggressively hunt and kill zombies, similar to multiplayer their jump attack insta kills a zombie on any round. Make them take 4 hits before downed and a pack of 15 would average about 100 zombie kills before been wiped out.
1500 kills no downs - juggernaut armour for 1 round and death machine in hand. Takes 12 hits to be downed, but speed is slowed right down. lasts for 1 round only and a good player could wipe out a round by himself in the 40's using this killstreak. 200+ kills.
2000 kills no downs - call in osprey gunner which drops perk care packages, 1 crate of each perk on the map, and kills all zombies that spawn and run into the chosen delivery room for 2 minutes
3000 kills no down - MOAB, clears one entire round of zombies. Pro players would obtain this in the 50's and use it for 1 round in the 60's/ 70's where they are extremely low on ammo
I'd wager most wouldn't agree with killstreaks in zombies but i think it'd be balanced - noobs would be able to obtain and feel achievement in getting sentry guns and napalm strikes while pros could aim for Ospreys and juggernauts.