WAR. War on big maps. Don't tell me WAR is hard, just do it, you are raking in billions, you claim to like the mode, make it happen.
Night time maps. Plaza doesn't count, I played it half a dozen times before I realized the sky was dark, but every square inch of that map is lit up like daytime. Real night maps like Nightfire from WaW and Hanoi from BO1, one of my favorites from that game
Weather. I loved the rainy maps, a snow map would be great- not just snow on the ground, but actually snowing. The wind in Vortex was really cool, both the sound and the debris flying around. The twister in the background was icing on the cake.
Size. I love CQB, I primarily use shotguns and pistols, but I don't need every single map to cater to one playstyle.
IF they bring back classic maps, they need to dig deep and bring back WaW maps. BO1 wasn't that long ago, if I want to play those maps I'll just play BO1. WaW is still an awesome game and I can still play it (for WAR mostly) but those maps with the modern guns and equipment would be great. Still, I prefer a focus on new maps.
Multi-Team Ground War. With larger maps comes the ability to make 5v5v5 games. There is already ground war in the game, so I am not sure why multi team is only 3v3v3, though I enjoy that being an option, as it almost feels like Face Off, which was surprisingly awesome.
New Voice acting. Sorry, I can't think about WaW without screaming Gary Oldman's voice in my head, along with Keifer Sutherland and the Japanese and German commanders. The voice acting has gone downhill since WaW, as there is nowhere to go but down after that tour de force, but these current Multiplayer commanders are so bad they take me out of the game. I'll be playing the game, having a good time, hear some boring announcement that may as well be the lunch specials in the cafetreria, and instead of running around shooting at people, I just think "ew, that voice is terrible".
The Sound director on this game should be ashamed, and not just because of the tatcical/sound whoring aspects people complain about, I don't give a damn about that, there is no artistry in the sound of this game. The music is generic, too.