Don't you understand that you don't have to be exact? You can use a single taunt for more roles. From its inception the current taunt has always been used as a gather and attack signal (or an annoyance).
Adding a wait/stop variation would allow for that one to cover the defend/retreat notification role.
A third one
So from jr2
1. "RETREAT!!" (or "FALL BACK!!")
2. "ATTACK!!" (or "CHARGE!!")
3. "INCOMING!!" (or "DEFEND!!")
4. "Flank!"
5. "Cover Me!!"
6. "Yes."
7. "No."
8. "Wait."
9. "I'm low on ammo."
10. "I'm low on health."
9 and 10 are out as you don't need to explain why you are going back, only that you are going back. So they fall under the stop variation 8. 1 and 3 also do not need to be specific since if you signalled 1 and don't fall back you're obviously not out of ammo and stating that your companions should prepare defense.
2 is currently fullfilled by the taunt (follow/attack), and 5, 4 are so locally obvious they don't need to be included.
Yes and no as a taunt seems silly. Use text for those.
I'm leaving one more taunt open since I'm sure we could come up with something to signify and call attention to something. Although even that could be fullfilled by a correctly chosen wait variation. Maybe fall back/defend is an option but then you should make the wait have other meanings as well.
It's like people making different binds for OM up, OM down. I had a single config. And when I transmit OM on the chat as a human you can sure as hell be certain it's up if we thought it down, and down if we know it's up. No need to litter the screen with it.
If I transmit OM as an alien and it's up you know the humans are going for it. If it's down and I transmit you know it's coming up or is under attack while building. All from a single bind over two teams in two opposing situations. That's how efficient binds are made. Not having to scroll through lists or having several binds which in essence do the same thing when you are playing with experienced players, which from my own experience are the only ones paying attention to team message and can correlate its contents to the situation.