One thing with DBPro and bone animated models is that texturing quickly becomes an issue, because you can't just texture limbs however you like, and having 2 different textures can really lock you out of being able to do anything with the model.
I think that for what you want to do, you should add little bits inside the mesh, like your suggesting you do - then make sure that when you UV map, you don't mirror anything, every polygon would pretty much need it's own texture space for this to work. Then, by pasting images on top of a models texture you can adjust it, like have the texture as a bitmap, paste your damage onto it, then grab it again and texture the object. This should work fine as long as your object only has a single texture, otherwise you can't just re-texture every time. You might find it's easier to just layer all the textures, like have the damage as the same size as the actual texture so for example, the damage done when the lower left leg is blown off could be pasted over all the other damage. Each time though your just pasting that damage layer onto the image.
One consideration might be the blend mode commands. If you plan to kill an enemy when he looses a limb, then this might work pretty neatly. If you add the damage texture for the relevant damaged limb as a blend texture, then you should be able to layer it so the damage sits on top of the original texture and does it's job practically instantly. You would have to experiment with the blend modes though - but remember that in the last update to DBP we got simplified blend mapping, so maybe that's the place to look next.
I think I did something similar, like I had a few variations of the enemy texture and swapped them out when an enemy died - not very complex and not ideal for showing damage underneath the mesh, but a more complex variant of that would probably work quite well - layering damage textures I mean.
