I've looked into it and a lot of shields in past civilisations came with spikes, sharpened edges and often came with large blunt objects attached. The Hoplites for example, an ancient Greek civilization, often fought with sharp edges on their shields so it could function as both a defensive and offensive weapon. In addition, many medieval styles of combat used a single-handed sword and a small shield called a Buckler, this shield was meant to function as a 'punching shield', sometimes sharpened, and not meant to take heavy blows but merely deflect them.
It seems like an interesting idea anyways, but I can't imagine it working with any current classes so a new class may be the better choice, loving the new concepts and animations by the way, what software do you use, Photoshop for the artwork I'm guessing but what about the animation?
Also, I've started a thread just around
multi-user abilities and formations, if you'd like to have a look feel free. ^^