I believe that there already was an epic battle between Littlefoot's mother and the sharptooth, but I know your definition of an "epic battle" is more warlike and probably involves more than two beings. I have to agree with Malte on the possibility of any sort of modern-style warfare in LBT without some sort of outside influence. It just doesn't really add up. The few fics that do have some sort of a Sharptooth army usually make the sharpteeth a fair bit more intelligent then they are portrayed in the series, or, in the case of my fic, having the fast-biters and smaller LBT carnivores perform a locust-like sweep into the Valley, or just a hit-and-run style attack for food. I would also like to add that the only reason the two prides in the Lion King 2 fought in a modern style was because of the slightly more civilized and structured nature of the two prides. Since the story was basically Romeo and Juliet with lions, Simba's Pride and the Outlanders basically acted as the houses of Montague and Capulet.