Hey there.
I just gotta say, im really hyped for this. Arma always needed a good dog.
So, i dont know what exactly you are planning on, but ill give you a few things, that i've filtered from real K9 units, that might be useful.
1. Bomb detection:
I'm sure you have thought about this and will be integrating something, but my point is to how the dog will react to it. You could add several behaviours. For one there would be sitting in front of the explosive and barking or if you want to be quiet, to have an audio signal for the operator, when the dog is sitting in front of an explosive. I dont have exact intel, but i believe a similar system exists IRL.
2. Attack:
Current dog builds resort to attacking and killing, which isnt really good if you want to catch someone. It would be better if the dog, instead of killing the enemy, would lock them in an animation. Perhaps there could be some damage, but not killing them.
3. Mobile dog:
For one, dogs in vehicles and helicopters would be really good, cause there needs to be a way to transport them. If you wanna go real crazy, you could make them able to parachute or rapell with their operators. At least, thats what they can do IRL.
Hope you can take some inspiration out of this. I'm burning to see the results of this mod.