Mega Bat Man

So in this latest episode of "Stuff I Want to See but Never Will Because....Life", I see all these rom hacks of Mega Man. Some even replacing Megs with some other character. So y'know what? How about we get a Mega Man fan game of Batman? Of all the franchises that would make a fun Megaman game, this one in particular practically has all the necessary elements you need gift wrapped to any programmer willing to take advantage of them.

The way I'd do it is have it play like a middle ground between Megaman and that one NES Batman game thereby allowing him to do that same wall jump he had in the latter, normally he would dash and dash jump like Megaman X does. His default weapon would of course be Batarangs, charged shots resulting in throwing three Batarangs at once that all do heavier damage. He would also have a secondary attack button that has him doing a powerful straight forward Bat Punch or damaging Slide Kick.
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Deadshot
STAGE: A Military Transport Train currently under control of the mafia carrying plenty of illegal contraband into Gotham.
BATTLE STYLE: Likes to use wall clinging tech to try and keep out of Batman's range and fire three to five laser guided rockets, will then drop down and try to bumrush Batman with dual machetes. Occasionally flings three grenades at once.
WEAKNESS: Bat Toxic, Bat Glue
WEAPON GET: Bat Sniper- The very laser guided rockets that can be shot in eight directions. 

Scarecrow
STAGE: The famed amusement park Wackyland home of the Tiny Toons, under this criminal's usurping rule it is now a twisted nightmare madhouse. 
BATTLE STYLE: With the arena filled with fear toxin, Batman is now hounded by slow moving ghosts whilst Scarecrow will take cheap shots with a pistol, if Batman is close enough Scarecrow will slash at him with a scythe. Will occasionally release a sudden strong dose causing Batman to imagine him as a freakish monster for a few moments. 
WEAKNESS: Bat Knuckle, Bat Crunch
WEAPON GET: Bat Fright- With a screen filling explosion of modified fear toxin all enemies on the screen see Batman summon a small swarm of homing nightmare bats. 

Firefly
STAGE: The Casino Strip of Gotham is even hotter than usual as several fire trap bombs have ignited setting much of the place ablaze.
BATTLE STYLE: A coward to the core he'll keep mostly to the air carpet bombing the arena below, only setting down when Batman goes upward to the higher plain and will thus take diagonal cheap shots upward. Will occasionally turn himself into a human fireball and dive down. 
WEAKNESS: Bat Sniper, Bat Fright
WEAPON GET: Bat Plasma- Used special Batarangs that now emit such intense heat energy they flat out erupt into flames upon impact.

Mr. Freeze
STAGE: A Nuclear Power Facility with all manner of experimental reactors and energy battery systems. And lasers, lots and lots of lasers.
BATTLE STYLE: Being quite the tank he feels no need to do any fancy maneuvering and will simply walk back and forth taking straight shots with his freeze ray, can even shoot diagonally upwards and will give a fierce punch when Batman is too close. Will occasionally shoot straight up causing ice spikes to fall from the ceiling or shoot straight down freezing the floor for a few seconds.
WEAKNESS: Bat Shocker, Bat Plasma
WEAPON GET: Bat Laser- A straight up copy of the freeze ray modified to even punch through shields.

Poison Ivy
STAGE: A Botanical Forest Reserve that has been closed off to the public due to a sudden case of giant man-eating plants and serpentine tentacles taking over the place.  
BATTLE STYLE:Likes to teleport about by letting her giant flowers "eat" her up and spit her out in new locations, all the while she attacks with organic gas grenades and a thistle whip. Will occasionally start running right for Batman just to grab onto him and kiss him with poisonous lips.
WEAKNESS: Bat Plasma, Bat Laser
WEAPON GET: Bat Toxic- A gas grenade that releases a large cloud of poisonous mist which deals continuous chip damage.

Jinx
And yes when I say "Jinx" I am specifically referring to the animated version.
STAGE: Titans Tower has been hijacked and it seems the Titans are captured making Batman the one who must navigate all of Cyborg's advanced traps and auto-defenses to reclaim the tower.
BATTLE STYLE:Using several acrobatic maneuvers to play keep away whilst firing off magical bursts of "bad luck" that turn the very arena against Batman.
WEAKNESS: Bat Fright, Bat Sniper
WEAPON GET: Bat Sparkle- Finding a way to combine magic and technology to replicate the magic bursts of "bad luck" that form nasty energy traps that remain stationary in the air, if an enemy projectile hits one of these traps that projectile is twisted into a homing shot that goes right back at the enemy!

Maxie Zeus
STAGE: Arkham Asylum has been taken over by the inmates and has been refitted into a rather beastly looking coliseum like maze of death traps and enemies seemingly ripped straight out a Castlevania game. 
BATTLE STYLE: Believing himself to be the very god Zeus he carries his own "Sword Of Olympus" which can fire off all manner of electrical bursts taking on either straight forward lighting bolt attacks or giant slash waves. Will occasionally charge at Batman ready to deliver a devastating uppercut or diving hammer slash. 
WEAKNESS: Bat Sparkle, Bat Fright
WEAPON GET: Bat Shocker- A straight forward energy sword weapon that uses intense EMP energy, very limited range but insane slashing power.

Killer Croc
STAGE: Oh great, a Sewer Level, probably the worst level in the game....
BATTLE STYLE: Will seemingly vanish into the mucky water and leap out without warning hoping to either slash with his claws or give one nasty bite. Will occasionally charge tackle back and forth relentlessly knocking Batman down from the wall. Also likes to throw a rock or two.
WEAKNESS: Bat Knuckle, Bat Shocker
WEAPON GET: Bat Crunch- A somewhat slow moving drill bomb that uses a giant pair of rapidly snapping jaws instead of a drill.

Clayface
STAGE: An Oil Rig quite a few miles from the coast of Gotham that is now being taken over by strange blob like creatures and abstract glob constructs.
BATTLE STYLE: After spending some time moving along the walls and ceiling throwing two to three sticky globs that can actually trap Batman in place for a few moments, Clayface will them split into three clones of Batman that will relentlessly run at the real one. Will occasionally turn into a speeding ball of clay that rebounds off the walls diagonally.
WEAKNESS: Bat Laser, Bat Toxic
WEAPON GET: Bat Glue- A straight forward glue shooting gun that fires off instantly solidifying globs of clay that form temporary platforms when they collide with walls.

Solomon Grundy
STAGE: A large Gothic Cathedral overlooking a massive acre spanning Graveyard. You'd think this zombie filled nightmare world would be the level that Scarecrow inhabited, go figure. 
BATTLE STYLE: Has only one strategy, relentlessly chase after Batman and try to beat the shit out of him and even try to power throw Batman into the walls or ceiling. Will occasionally cause deathly hands of the dead to rise from the ground at random locations to try and grab onto Batman. 
WEAKNESS: Bat Glue, Bat Sparkle
WEAPON GET: Bat Knuckle- A forward dash attack using a rocket powered pile bunker gauntlet, can even be used in the air resulting in an air dash. Weapon energy is only spent when it actually hits an enemy.
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Yeah I'm borrowing a bit from Megaman 3 here. After the initial ten "Criminal Masters" you'd have to revisit some modified versions of previous stages fighting the AMAZO Android.

AMAZO 1
STAGE: Nuclear Power Facility
BOSS: Copy Data Superman- Will fly about the screen at diagonal paths firing heat lasers and occasionally striking the ground with a power stomp. Will also try to use a powerful charging fist and rising uppercut.

AMAZO 2
STAGE: Wackyland
BOSS: Copy Data Blue Beetle III- Deploys spinning blade projectiles and rocket powered sword dashes, will also try to use a powerful proton cannon attack.

AMAZO 3
STAGE: Titans Tower.
BOSS: Copy Data Starfire- Will slowly fly about after Batman firing green fire bolts, will suddenly erupt into green flames and fly fast while carpet bombing the floor.

AMAZO 4
STAGE: Arkham Asylum
BOSS: Copy Data Wonder Woman- Uses a sword, shield and golden lasso for attack, leaping across the arena trying to out pace and out maneuver Batman.
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The last level would be a large militia controlled castle built on an island somewhere in the Bermuda Triangle. Here Bane awaits with a full arsenal of nuclear warheads that make him an immediate international threat. And instead of a standard boss rush it would have the "Criminal Masters" sprinkled about the four stages at key locations.

Bane's Castle 1
STAGE: Arriving in the Coastal Jungle that leads into a mysterious Old Temple, these ancient catacombs are the ideal alternate path for which Batman can bypass the heavily guarded outer gates of the castle.
BOSS: The Guardian- The cyclops awaiting at the end of this underground odyssey. Instant death awaits Batman should he allow this beast to even see him. 

Bane's Castle 2
STAGE: Leaving the last remnants of the Old Temple and going right to the Outer Hangar where many of Bane's acquired war machines are stored and being primed for battle.
BOSS: Deathstroke- A battle taking place atop a flying harrier jet, Deathstroke using his swords and guns to try and force Batman off to his doom.

Bane's Castle 3
STAGE: A rather unusual Medical Wing that can't decide if its a dingy blood ridden torture dungeon or a makeshift super girly theme park with quite a lot of pink.
BOSS: Harley Quinn- Pilots a giant alicorn mecha that deploys all manner of robot critter drones to keep Batman from focusing on the main threat.

Bane's Castle 4
STAGE: The Weapons Development Lab where not only are the nuclear warheads found but a whole maze of experimental weapons and death traps await. 
BOSS: Joker- Forces Batman to tackle an entire room of death traps to try and reach the main control panel.

Bane's Castle Final
STAGE: The Hallowed Bastion, an entire hauntingly beautiful castle that looks ripped straight out of a Kingdom Hearts game where the ultimate challenge awaits. 
BOSS: Bane- At first uses a freakishly huge and regal looking battle knight mech to try and blast Batman into oblivion, thew very hands it uses to try and crush him could prove to be its fatal weakness. If the mech should fall then Bane will abandon it and fight Batman man to man with fists and power spiking venom.