I have strange playmates.
Our idea of a fun time involves what if experiments that go into borderline impossible fan fiction, or casting books we really want to see on the screen
For instance, there's one thought experiment that asks a simple question: What if Batman entered Spider-man's New York City? And what if Spider-man ended up in Batman's Gotham at the same time?
The first thing Batman would do is start building his new identity. Sure, he can cook up Bruce Wayne as a "fake" ID, and he'd then have to start rebuilding his fortune from there. And he'd probably end up with owning half of the Fantastic 4's Baxter Building, a good chunk of Stark Industries, and maybe even part of Black Panther's Wakanda. Where would he get the money for these investments? You mean that there isn't enough room in his utility belt for a million dollars in diamonds et al? Hell, he could patent some of his toys from his belt, and trade the patents
to Tony Stark for stock options.
Or, Batman could do what the DEA does, and simply confiscate property of criminals when they can't be returned them to their proper owner. Either way, he wouldn't be hurting for money.
Option #3: Batman would go to Avengers Tower, or the Fantastic Four, and say "Hey, look, guys, I'm a superhero from another dimension. I need to get home, got any ideas? Can you help a brutha out?" At that point, Mr. Fantastic would get to work cycling through dimensions until he gets the right one (creating no less than six word-threatening crises), and Stark would probably let Batman play with his toys to build an Iron Bat suit (which I presume is what Batfleck is wearing in the next Superman film) so he can kill time.
After that? Can you imagine Batman resting on his laurels? This guy is more OCD than anyone else on the planet, as far as Superheros go.
VILLAINS
The first and most simple aspect of this shift comes with the villains. Batman generally doesn't have to put up with super villains, but Spider-man has to on a daily basis.
Lizard or Rhino: I grouped these two together since they're basic muscle. They're also similar to other Batman villains: Killer Croc, Solomon Grundy and Bane. This is actually easy when you consider it. Batman doesn't have to deal with Bane all that often, but when Bane was written as someone with a brain, Batman beat him every single time except for their first encounter. But if you transplant Batman into Spider-man's universe, what do you get? Batman has to deal with either the Lizard or the Rhino, neither of which usually has a brain (the Lizard has his moments of having an IQ, but generally, he's just an animal with a Jekyl and Hyde thing going on). They would be easy enough. Expect Batman to lead either one of them into a building, and then drop it on them.
Sandman -- Another easy one, really. Yes, Sandman can't be punched, or killed, but, heck, neither can the shape-shifting Clayface. And, knowing that Sandman is essentially immortal, Batman would probably just bring along incendiary devices to turn Sandman to glass.
Black Cat -- I'm not even sure that Black Cat is a villain anymore. She's a sexy cat-burglar in black leather who flirts with the local superhero ... oh, screw it, Batman already has enough Catwoman issues. Also, Black Cat would find Batman boring.
Vulture /Green Goblin -- two flyers that deal with projectile weapons, usually daggers or pumkin bombs. Yeah, Batman
never has to deal with someone like that. However will he manage with ...
Oh, wait, Batman's dealt with Firefly. If you're not familiar with the comic book version of Firefly, imagine a pyromaniac who can fly like Vulture, hover, and comes with firebombs and a flame thrower, as well as close quarters combat. Yeah, after dealing with this nutcase, Spider-man's flying killers will be almost easy.
Electro -- Batman will have a rubber-insulated Batsuit and break every bone in Electro's body. Then he will throw Electro into the Hudson river.
Venom / Carnage: These guys might be a problem, since they're both older characters, and experienced. They're crazy, but they're not stupid. Sure, they're both allergic to fire and sonic weapons, and Batman will get firebombs to slow them down, and sonic grenades and weapons installed on whatever toys he brings into Marvel's Manhattan, but it's going to be a stamina game. Carnage would be pelting Batman with numerous projectiles and melee weapons, and Venom can close quickly. If either one got their hands on Batman, it would be game over. This would be an argument for Batman to have a pseudo-Iron Man like suit, even if it's a basic exoskeleton. Why would fire and sonics not be an easy out? Because last time I saw him, Venom was getting used to sonics over time. In either case, it would require a combination of both sonics and melee moves to cripple them.
Mysterio: Mysterio is a master of illusion in the Marvelverse. But, Batman has has his brain rewired by both the Mad Hatter
and Scarecrow, a fancy laser light show wouldn't mean anything to him. Also, he's have specialized filters in his Bat suit.
Shocker .... I won't even go into Shocker, since even Spider-man makes fun of him.
Chameleon: Chameleon is a spy in the Marvelverse who has fancy tech that makes him look like anyone. He's not a supervillain, just a guy with fancy toys. This would require detective work ... from the world's Greatest Detective muahahahaha
Doc Ock: This would be interesting, for the simple reason that Doctor Otto Octavius is quite smart, but if you can get your hands on him, most women I know could beat him to death with a baseball bat ... but you have to get past his four indestructible mechanical arms. That means that Batman would probably just go all predator on him, pick off his guards one by one, then drop out from the ceiling, straight onto his head. Or concussion grenades.
Kingpin: Batman would, for the most part, probably just make a deal with Kingpin. He would have a few run-ins with Kingpin, breaking apart illicit parts of his criminal empire. They would go a few rounds. Batman would break a few bones. After about a month, they'll have a nice polite sit down, in which Batman will tell Kingpin that he's going into white collar crime from now on. This is a deal he's more or less got going with the Penguin, who, in the comics, runs his own lounge, and more or less sticks to money laundering, information brokering, that sort of thing.
What happens when Batman meets the rest of the Marvel-verse? He'd either ignore the Avengers, or try and take it over ... like he did with Justice League.
Well, he'd try
Let's face it, in Gotham, Batman is the big fish in a medium sized pond. Yes, I said medium-sized; Gotham was always the city with corrupt cops, corrupt city officials, overrun by the mob... you know, Chicago. And, since Chicago is the second city, well, Batman can keep it.
However, New York? Batman couldn't run two blocks without running into yet another superhero. They even break down some of them by neighborhoods.
The X-Men have Westchester (far enough out of NYC to avoid the city line, but close enough for a commute), so probably the Bronx. Daredevil has what used to be called Hell's Kitchen. Tony Stark is on 59th and Broadway, just off of Columbus Circle, the Avengers have Central Park East covered (890 th Avenge). And the Fantastic Four (when they're in town) are off of 42nd and Madison, and SHIELD has a station at 59th and Madison. Midtown is covered. Luke Cage has Harlem (depending on what's going on there at the time), or the GEM/Amc theater on 42nd street.
Spider-man seemed to have the other burrows (let's face it everyone, he lived in Forest Hills, Queens). However, his newspaper seemed to be the Flatiron building, in lower Manhattan, so he has a swath to himself.
You think Greenwich Village isn't covered? Doctor Strange lives on Bleecker Street.
Batman would either have to learn to play well with others, or move to Brooklyn. Or worse, Staten Island. Though, being Batman, he might want to move into the Bronx and take it over.
Meeting Tony Stark.
Ah, but what happens when some superhero gets cloned, or brainwashed, or turned into a villain? Shall we count the amount of people that's happened to in Marvel? Like Daredevil being possessed, or Wolverine being brainwashed, Captain America having his own twin and his own clone, or the 500 Iron Man knockoffs, or Deadpool being Deadpool....?
You get the idea.
Not to mention the "misunderstand" fight -- that's two superheroes running into each other, either or both thinking that the other is the badguy
Wolverine / Daredevil -- Batman would win against both of these men with heightened senses, and for the same reason: he'd bring itching powder.
Captain America: Batman vs. Captain America was already seen in a Marvel vs. DC crossover event in the mid-90s. They'd be very evenly matched, and it would end in a draw, probably a double-KO. But that's if it's Captain America -- if it's a clone, or a twin, or anyone other than Steve Rodgers, Batman will probably win on the grounds of stubbornness
Doctor Strange: Batman would have a nice, calm, reasonable conversation with the good Doctor, and not piss him off.
The Vision: Batman deals with the Red Tornado, the DC comics version of Vision, every other day. He has a plan to kill Red Tornado (and everyone else in the Justice League, really) so he'd probably use that on Vision.
I could continue, but this is already over-long.