Overall, I VERY much like your idea. Only a few qualms.
Like Shelly, I also have to contest the clown ball. To me, it could be something tossed out of the Magic Wand (just like when Lemmy did it). Whether it be thru GW-style "random" effects, or maybe you can charge up, and try and get the specific spell you want, through "Playstation Button Magic". 
I saw Morton and Larry spinning their wands stylishly in NSMBWii, before casting a spell. The "charging" mechanic could work well in this kind of stance.
Haha, very well, I will switch around the Up B move to the Recovery Shell one then, and put the Clown Ball as one of the Forward B items.
The other thing is, size differences. You can try and get away with making a number of the Koopalings pallete-swaps, but Lemmy is technically supposed to be QUITE smaller than the rest of his siblings (and he's actually the second oldest too. Poor thing. 
). On the other hand, since Bowser can range in size depending on the game, maybe I'm over thinking...
LoL, this is why I clearly said, "Lets just assume they're the same size for the sake of putting them in the Bitchslap!
Finally, I would propose a bit of an interesting thing that could be used to cite another game. In their appearance in M&L:SSS, the Koopalings were accompanied by a very powerful Bob-Ombs to help them deal with pesky plumbers. Maybe, randomly, your "Fake Koopa" trick could sometimes result in enemies getting the [parasitic bomb] BLOWN out of them, because Lethal Bob-omb might pop up, instead of just poofing for minimal damage. I figure a 1/8 ratio would be fair enough for this kind of thing, since this type of attack stands to be VERY good, any way!
Hmmmm, seems like a good idea to me. Very well then!
Posted on: July 13, 2009, 11:21:55 PM
Okay, since I've already done my fair share of characters, I'll try to impart some of my Stage Ideas. I'll also put what music I think goes with each stage as well. Heh, hope you enjoy.
Stages
Battlerock GalaxyINSTANTLY banned among the tourneyfags, Battlerock Galaxy, IMO, would be just a super fun representation from Super Mario Galaxy. The stage is basically just one big moving platform, which moves around the Battlerock. The same hazards from Battlerock are still there, including cannonballs being fired towards the platform, lightning gates that have to be jumped over, etc. The true catch of this stage is that just like in Galaxy, you can stand upside down on the bottom of the platform. Mind you, you can still be spiked off the stage and such, but if you manage to jump back, you will be upside down on the platform. Heh, I'm not sure if it can be done, but I think with a proper gravity field effect for the platform, it can be, and it would also be tons o fun. The important thing is that they try to make my stage a reality.
MusicBattlerock Galaxy - Super Mario GalaxyGood Egg Galaxy - Super Mario GalaxyGusty Garden Galaxy - Super Mario GalaxyBuoy Base Galaxy - Super Mario GalaxyMelty Molten Galaxy - Super Mario GalaxyBattle For The Grand Star (Final Bowser Battle) - Super Mario Galaxy
Level 7/Level 27/Level 56I have yet to write about their character bio yet, as I'm still fine tuning them, however I've always had this stage in mind from Bubble Bobble. Just like the Fire Emblem stage, Castle Siege, this stage combines three stages from the Bubble Bobble game. You start on Level 7, then as the EXTEND Bubbles are popped, you move to Level 27, and the same from Level 56. The EXTEND bubbles MUST be popped as well, or else Baron von Blubba will appear and start attacking everyone on the stage. These stages will also include Fire, Lightning & Water bubbles as well. LoL, oh this stage will be banned too....*in Chris Rock voice* BUTWHOCARES?
MusicBubble Bobble Theme - Bubble Bobble (No remix either. IT HAS TO BE THIS VERSION)
Puzzle Bobble/Bust-A-Move Theme - Puzzle Bobble/Bust-A-MovePuzzle Bobble/Bust-A-Move Theme 2 - Puzzle Bobble/Bust-A-Move
Avalanche AlleyFrom 1080 Avalanche comes Avalanche Alley. This stage is similar to Melee's Super Mario Bros 2 stage (which should be brought back too). The stage is essentially a half-pipe, so no spike deaths here. During the stage, random 1080 Snowboarders will come down the half-pipe and you'll see them coming towards you. Also, an avalanche will also be coming towards you, so if you are in the half-pipe when it comes down...ouch.
MusicGolden Forest - 1080 SnowboardingBlue Flame - 1080 SnowboardingCall Me - 1080 Snowboarding (oh man I might catch flack for this one)
Akari Hayami's Theme - Wave Race: Blue StormStrongwater Keep - Wave Race: Blue StormLost Temple Lagoon - Wave Race: Blue Storm
Stone Temple TowerSimilar to the Metroid Prime stage, Frigate Orpheon, this stage takes place on the outside of Stone Temple Tower and will invert during the course of the match. The only difference is that, the regular level will not allowing spiking, and when the level is inverted, you will not be able to kill upward, due to the regular level's floor being in the way.
MusicA mix of
Stone Temple Tower &
Stone Temple Tower Inverted - Majora's Mask (Still my favorite Zelda Dungeon theme ever)
Ballad Of The Wind Fish - Link's AwakeningThe Indigo-go's Song - Majora's Mask (from 0:18 - 2:04, and I want a Jazz remix of this song)
Stallord Boss Battle - Twilight PrincessA mix of
Light World Dungeon &
Dark World Dungeon - A Link To The Past
ReznorThat's right, Reznor. Just one long Platform that disappears from time to time, and one giant spinning wheel with 4 platforms. That's pretty much it!
MusicKoopaling Boss Fight - Super Mario WorldBowser Boss Fight - Super Mario WorldSpecial Zone - Super Mario WorldLuigi Blew It Underwold - Super Mario Bros. 2Stage Boss - Super Mario 64
Airship FortressNow, I kinda wanted to make this stage scroll along, like it should, but eventually it'd have to end, so sadly I don't see how it's possible. Anyway, this stage will have the standard Airship hazards, and of course the moving screws along the bottom, cause really, they have to be there.
MusicKoopa's Road - Super Mario 64Overworld 2 - Super Mario Bros. 3Fortress - Super Mario Bros. 3Bowser Battle - Super Mario RPGWario Battle - Super Mario Land 2Boss Battle - Super Mario Land 2
Mining MelancholyThis would be similar to the 2nd DK level in Melee (the one with the DK Rap), in terms of platform design. Added would be some Krow's dropping eggs, some Kiingers dropping down, and hooks that players could grab onto just like they would a ledge.
MusicMining Melancholy - DKC2 Diddy Kong's QuestHot Head Bop - DKC2 Diddy Kong's QuestDisco Train - DKC2 Diddy Kong's QuestFunky's Flights - Donkey Kong CountryAquatic Ambiance - Donkey Kong Country (...Okay, not really fighting music but....screw you)
Park SlopeFor those unfamiliar with NYC, Park Slope is in Brooklyn, NY and it is where Doc & Little Mac are running when training, with the Statue of Liberty in the background. This would simply be one flat long stage, like the Bridge of Elden from the Twilight Princess stage. No real hazards except for dropping items and such.
MusicFight Theme - Mike Tyson's Punch OutTraining Theme - Mike Tyson's Punch OutSuper Punch Out Medley (Bear Hugger, Mr. Sandman, and Aran Ryan would be my choices)
Minor Circuit Fight Theme - Punch Out WiiMajor Circuit Fight Theme - Punch Out WiiWorld Circuit Fight Theme - Punch Out Wii
Planet VenomAnother one of my instantly banned stages, this stage would completely consist of the classic SNES FX Polygons, which would make up random & different platforms with how often they switch around Obviously, some kind of warning would take place before such platform madness happened. OR WOULD IT?
Music Venom Base Level 2 - SNES Star FoxCorneria Boss - SNES Star FoxTitania - SNES Star FoxTitania Boss - SNES Star FoxFortuna - SNES Star FoxMeteor - SNES Star Fox
These aren't the only Stages & Music Choices I have in mind, so I'll post more later. Also, some of these songs might not be fighting worthy, so I would hope that the ones that aren't are remixed and such to be fun to Bitchslap too.