I'd go for 2 ring menues, like in Left 4 Dead or Battlefield 2 (if I remember correctly)
Hold button to open up an menu, drag the mouse in the direction of the sound you want to play and then release the button.
Works quick and efficient.
I'd use 2 to make sure it does not becone to crowded, or else you will send wrong commands to often.
Example: menu 1 is used for important "in combat" commands, it only knows 8 commands.
Up: Press forwars / Rush the enemy (general "attack" command)
Up/Right: Passive units incoming / Enemies are flanking
Right: Retreat / Disengage the enemy
Down/Right: Need backup
Down: Hold this position / Keep them at distance (general "defend" command)
Down/Left: Need support against "soft" targets (calling AA and anti-BA, since a unit good against ASF is generally good against BA, too)
Left: Have to retreat / Returning to base
Up/Left: Artillery incoming, go passive!
The second one might have more, even 16, commands.
The sounds here are not supposed to be used while fighting, so you can take more time selecting the right command. This makes a cluttered menu useable.
Things that go here could be:
"Need spotter" / "Need NARC/TAG"
"Spotter ready, need fire support" (Hey I have a NARC, and I will use it)
"Shazbot" (I <3 Tribes 2)
"APC in position"
"Yes" / "Aff"
"No" / "Neg"
"I need some money"
"Gathering lights/meds for raid"
"Need Elementals for a point"
and so on