If I'm wrong and this is already doable, then correct me!
Well, currently there are "selection" and "command" sounds per unit, which is fine. However I think it could be good, if every command could have its own sounds. For example, if I have Archmage unit, the "move", "static fire", "ice nova" could have its own sounds. I'm not meaning this should be added to the MagiTech tech tree, but as an overall feature.
I came across this when I was designing the style of the units. Some times, the command sound for attack for example would not sound good during move. And if there are some epic abilities, then it could be great if they could have their own sound effects.
For example, within my first faction I came across following:
Spec Ops: "This bullet has his name" would sound good with the attack command, but rather out of place with movement command.
Advocate of Supremacy: "For the Emperor!" This sound effect could be in move/attack, but this unit has a special ability "Will of the Emperor", so it could be just more epic if the "For the Emperor!" phase would be said only when the WoE is activated. The unit is anyways elite and in very high in tech tier.
Interceptor: "Target lock in" also for attack, not very good for just attack-move.
Also, when an unit is finished and pops out from building, it could have some sound effect. Like the legendary Terran Marine in SC1 (You wanna piece of me, boy?). But this latest was discussed in some other topic.