I'm not sure if these are overly suggested but these three things I find seem to be missing from this game.
#1 ~ I think that Your character should be able to swim.
This may cause lag though because Maps would also have to generate underwater structures.
# 2 ~ Water should break fall damage.
This could add a whole new concept to AoS. Diving from a great height into water.
#3 ~ Achievements.
Not a whole lot to this. 100 kills, 50 kills, 25 kills, 1st kill. (So on and so forth)
#4 ~ Server mod.
This means that if the "Owner" of the server has a mod (Speaking mainly to firearms), the whole server is granted with the modded guns for that game only. Of course after a little extra loading.