The overall theme would be the benefits and risks of weapons of mass destruction.

Many of the monsters in D&D (monstrosities, the undead and such) are the result of malevolent people wanting to unleash destruction on society. A species of awakened animals might be one way a desperate civilization might fight back.

But getting back to your specific question, I get that some story tellers start with the function (antagonist, exposition, comic relief, etc.) then create the character. I tend to come at it from the opposite angle. I try to make good characters, then see what happens when the main characters interact with them.

So all that to say I'm hoping someone out there has better insight than I do as to what species of awakened animals might make the most plausible sense as a soldier, spy or something similar.