3The People Building and Delivering the Bat-Gear Would Know, Too
Now, you may be saying that, sure, the people swarming over the Wayne Manor construction site may all notice that Bruce has demanded a huge, elaborate basement/cave. But that's all they'd know. They'd have no reason to realize that 1) he's going to use that space to fight crime, and 2) this indicates he is, in fact, Batman.
But the basic floors and walls and lighting of the cave are just the tip of the iceberg. What is he going to put in there once he gets the foundation built? Obviously not everything that comic-book Batman had in there.
Comic-book Batman had a two-story Lincoln penny, a life-sized T-Rex doll, a jet, a helicopter, a gym, a computer, a mechanic shop, an interrogation room and other trophies and wonders. But that's comic-book Batman. We're talking about Bale Batman here. So, say he has the minimum. So, like a Batcomputer and that's it? We already know what his computer set up is. We've seen it:
"Man he's going to ask me to reassemble these in that stupid cave. I better come up with a reason to quit."
But he also needs a place to fix his car -- he goes on police chases and crashes through walls every time he takes it out, so he's got to change the tires somewhere secret, right? So he's got to have one of those workshops like on Pimp My Ride down there. At least. Then, assuming he doesn't have just the bare minimum, he's probably also got the forensics lab and a workshop where he builds his gadgets -- you know, the stuff he had in his temporary setup in the last film.
All of that must be custom made, then delivered and installed. And it gets to be kind of hard to keep up any kind of a cover story when you notice Batman's love of branding.
"Hey Mr. Wayne, where do you want us to put this giant Batman symbol illuminated floor panel? Does it go by the crime supercomputer or by the floating island with retractable bridges where you keep your black tank?"
But even the guys who don't actually handle bat-shaped furniture deliveries aren't going to have to be Sherlock Holmes to put the pieces together. This guy is demanding a huge cave facility, wired up like NORAD, with all of the entrances hidden, and is (presumably) demanding non-disclosure of this fact by everyone who works on it. Either he's Batman, or he's a terrorist.
But, OK, maybe if he plans really carefully he can compartmentalize the project so that no one guy sees everything. Maybe he uses a separate crew on the Batcave, and make them use an off-site entrance, like the hidden entrance away from the house that every Batman uses for the Batmobile. Then, only once they're finished, does he cover up the entrances and hire the crew to build the manor itself on top of it. And all of the people involved in the Batman parts have to sign an agreement not to tell anyone.
Because construction workers are known for their absolute discretion.
OK. Unfortunately, even then ...
2Bruce Wayne's Full Time IT and Janitorial Staff Will Know
The primary purpose of the Batcave in every single incarnation of the character is that it's the command center for Bruce's crime fighting operation. There are many monitors and computers and scanners and communications equipment, and behind each you have servers and routers and high-speed internet connections. According to the character's mythology, the Batcomputer is on par with the FBI computers. And, it'd have to be -- he's doing the same job. He needs access to the same criminal record databases, etc.
The difference is the FBI has entire rooms full of people who do nothing but maintain their systems. Somebody who knows where each network cable goes.
So who's going to handle Wayne's Internet security, and program all of his proprietary software? He doesn't just have Windows 7 Professional on his Batcomputer. Otherwise, what use is it?
"Ok, Mr. Wayne, so you need our best system, only with bat logos everywhere. And we can't tell anyone what we are working on. No problem!"
And this equipment will break. Even if Wayne wasn't the target of every criminal hacker in the world, the Batcave itself will do the damage for him. It's a cave. There is standing water everywhere, and more dripping from the ceiling.
You can never completely keep the moisture out of the systems, and that means corrosion. Also, there are insects, rats and other rodents, the kind that like to chew on electrical wires and data cables. Not only do you need IT staff (constantly, every time something malfunctions) but you need exterminators working around the clock. You're asking for an infection or disease otherwise.
And that's not even talking about the everyday maintenance that would come with a facility located in a huge cave. For one, you have the bats. Thousands of bats shitting on all of your stuff all the time.
Yeah, that's guano in an attic from a couple of bats. The cleaning work would never end. Who's going to do it?
Then you have all the other moisture-related problems, like mold, and mosquitos breeding in the stagnant water. If you use pumps to keep the standing water out, then someone has to maintain the pumps. If you run massive dehumidifiers, someone has to maintain those. If you run air filters, somebody has to change the filters. And that's just the special, cave-related stuff -- you still have the routine issues with plumbing and wiring and climate control that you would get in any building, each problem requiring a contractor to go inside the Batcave without a blindfold.
So each guy, what, signs the same non-disclosure agreement as the construction workers? That's fine as long as you can threaten them with firing if they disclose anything. But what about after they leave? What's to stop them from blabbing to everyone who'll listen about their job working in Bruce Wayne's Batcave?
"You bet your ass I'm posting the blueprints on Facebook."
It's at this point you realize ...