First, the officials' business entity has insurance - and that pocket will be deep.
Second, it will take a lawsuit and discovery against the officials to generate enough evidence against the NFL to pierce the assumption of risk defense that the NFL enjoys.
So the strategy would be first to sue some officials individually and/or their association/union, and anticipate that the officials will say they were instructed by either their union/association or by the NFL itself not to call certain violations, even tho they’re written in the rules?