This is my personal opinion:
Killstreaks
I personally am not keen on killstreaks, however I definitely believe that AOS should have a killstreak counter so you can see your highest killstreak (for that game of course, unless they add some type of account integration). Pyspades can provide rudimentary killstreaks for those who want it.
Weapons
Keep them as they are. Three weapons is fun and enjoyable, adding more would be boring- you just end up with 50 weapons which do the same thing. If weapons are going to be added they should be interesting things which serve their own role (like I don't know a RPG- not that it should be added, rather that it would be different not just a SMG with slightly longer range).
Classes
Nope. Just choose your weapon- no biggy.
Leveling
Once again: Nope. I don't want to simply level up to 80 then restart and do it again. Over. And. Over.
Graphics
I would much rather be looking at AoS's colorful graphics than CoD's dark ones. I do think (optionally of course) that things like DoF bluring and Mipmaps should be added just to give it that extra touch.
Linux and Mac
I actually don't know what AoS uses but I think we should look a cross platform graphics library (if we don't already use one) like OpenGL so AoS can be ported to Linux and Mac. As these OS's don't get many games you may see a lot of coverage from them (this was an observation made by another game who found that %50 of their users were Mac and %10 were Linux). Oh and if AoS is written in C# Mono seems to do the job (once again I know nothing about AoS's internals).
So those are my personal thoughts