Cranston's character was brilliant, commanding and the emotional core. Taking him out early was the film's biggest flaw, one that did hurt the film overall. The movie could have been one of the best sci fi blockbusters ever, were it not for that mistake. But, they can redeem this mistake. It's far fetched, but can work. Make it so that the government made it seem as if he was dead, through the use of chemicals so that Brody would go on to help in the fight to save ourselves from Nature's wrath.