A more satisfying endgame

In addition to leader legacy endgames, it would be satisfying to need to destroy a “queen” plague heart that is embedded in some sort of maze-like building or cave. It’s protected by a host of zombies. We need bolt cutters and welding torches to access parts of it. During a game playthrough we can find various parts of “super” plague weapon that is required to take down this “queen.” Maybe we find clues to the locations of the parts of this super-weapon on the bodies of plague researchers.