In Lord of the Flies, William Golding uses his characters to represents different elements of personality and creates a microcosm of society. Ralph is charismatic and is the natural choice for the boys, possessing qualities that ensure that he is voted leader. The conch or "trumpet-thing" immediately attaches a sense of order to Ralph. On the other hand, Jack assumes he will be voted leader and he represents a less than democratic approach, expecting the boys to vote for him because he is "chapter chorister and head boy." Simon and Roger represent the two poles of goodness and wickedness and Piggy represents the rational and scientific approach, always reasoning and measuring the boys' current circumstances against what "grown ups" would do in coming to a conclusion. Without Piggy, the boys would be less likely to manage the power struggle between Ralph and Jack and this would have probably split the camp from the beginning.
To be a hero in the classic sense, after having suffered this traumatic event of being stranded on a deserted island, Piggy needs to be accountable to a different standard with unique character traits. He does have qualities that the other boys lack, which make him unpopular and which set him apart as he is the closest thing to an adult on the island and the boys resent his sensible approach. Symbolically, after Simon's death, Piggy becomes another sacrifice when civilization finally deserts the boys and, as the conch shatters, Piggy falls to his death, ending all hope that the boys can recover from this situation of complete brutality and bloodthirstiness that now exists. Accordingly, Piggy could represent a hero, having recognized Ralph's potential and having proved himself countless times by encouraging Ralph along the way.
One could also argue that Piggy, once heroic in principle and reason, fails miserably as a hero in Chapter Ten with his pusillanimous and disloyal ignoring of what the hunters do to poor Simon, the Christ-like figure. The next day when confronted by Ralph, in his cowardice much like that of St. Peter, he excuses himself and denies Simon, insisting that they did not see anything.
"We was scared!" said Piggy excitedly. "Anything might have happened. It wasn't--what you said."
Ralph knows that Piggy is lying to him and has "loathing...in his voice" as he tries to give Piggy another chance to be truthful and have integrity. Instead, Piggy attempts to excuse himself: "It was an accident." But, Ralph knows the truth and when Piggy touches him on the shoulder, Ralph "shudders" at the touch of the boy who was once his friend: "The air was heavy with unspoken knowledge." After this cowardly act of Piggy's, Ralph distances himself from the physically and spiritually myopic boy. For instance, he stands back from Piggy after borrowing his glasses to start a fire. Sensing Ralph's loss of respect, Piggy speaks "moodily" later in this same chapter.