Alternate Kung Fu for TSR's Marvel Super-Heroes
Martial Arts ABCDE are now Martial Arts. When you are investigating something or moving or attacking or defensing you get to roll an additional 1d10. Whatever the die shows you get that many extra words to describe extra side effects and flair to your actions. You don't just notice the ancient coin on the ground, you sense a disturbance in the local chi flow. You don't climb the building, you double-jump all the way up like Vega. You don't just dodge, you spin over your opponent's head. You don't just kick the mugger, you redirect the knife in his hand toward his accomplice.
Alternately you can add the value to your roll like a free source of random karma.
Checks: limitation on number of words you can use to describe; GM has final say as to whether or not this sounds like something from a Chang Cheh movie and if not she has final veto; if you attempt to duplicate the effects of another super power in your description it is rolled at Shift 0 unless the GM decides otherwise; this ability recharges in combat only by being hit or attacking a different target, only works once per task per session outside of combat.
Advantages: you can differentiate martial arts users your own damn self without relying on a book mechanic; you don't have to choose whether to be good at hitting hard or hitting fast or whatever; literally everything in the game gives you a +1CS option so martial arts as-written are very gamey but not that exciting; removes the tendency for Pathfinder style overspecialization whenever a fight breaks out, guys who are only good at grappling just circling the fight while their friends are cut to pieces waiting for an opportunity to grapple...
Disadvantages: +1CS is incredibly simple to remember and adjudicate where this will require constant policing.
Methods of augmentation might include: allowing characters to gain Bonus/Penalty words as an alternative to normal karma awards for kung fu specific role playing (honoring your master, desecrating a shrine, meditating with a specific item as a focus, disrespecting your opponent); allowing characters to just do the 1d10 thing outside of combat and keeping the +1CS in combat; keeping the 1d10 roll as just a random kung fu karma-like bonus in combat and not worrying about anything else; allowing players in individual initiative to use their 1d10 roll to swap places in initiative at any time, potentially acting multiple times per round.
The great thing about this honestly from a story perspective is how easy it is to reward and enforce. Someone trying to abuse the system? Their system gets blocked by bad chi, they get their way this time but they're unable to use this ability until the re-center themselves or atone or do a side quest. Boom. Someone actively seeking out new training and new masters and secret breathing techniques? Bonus words.
What of Martial Supremacy? That's straightforward: like a D&D monk, that's just the level of superhuman/paranormal defense your kung fu is capable of ignoring. You have Martial Arts and Martial Supremacy Excellent, you Twisting Grasshopper Elbow the guy wearing the Amazing armor, his armor only protects like it's of Typical strength.
Alternate Kung Fu for D&Dalikes
I want to get away from the Terms mostly because I feel like D&D classes get just albatrossed with vocabulary over the iterations. People coming fresh to the game are going to look at a first level monk and go "Oh I can be Jackie Chan in Middle Earth? That's weird but I'm game, Jackie Chan is awesome." Longtime graph-mappers on the other hand are going to go "Oh let's see how they handle unarmed damage proficiency and progression, unarmored AC bonus progression, monk weapons, Flurry of Blows, Stunning Strike, slow descent, disrupting strike, talk to animals, uhhh ki pools, ki foci, style/school traditions/paths, movement speed increase and progression, thief skills, magic resistance...."
You also get to answer the question of whether kung fu is something to reserve for the monk or something you can layer on top of any class so that everyone is kung fu wizards and ninja robbers. This is more a distinction for D&D2 and earlier, since later models all have something like feat paths or multiclassing-as-core-assumption or class feature pick-em options and stuff that can let almost any class feel like almost every class.
So you get this list:
Roll to hit
Other Combat Round Action (like casting a spell or using the Dodge or Help features in 5e)
This is a standard set of rolls. When any character learns a school of Martial Arts the DM chooses one item off of this list. Whenever the character does that thing they may do it twice. The DM controls what kinds of manuals or masters you can find so they can police this a bit; the most imbalanced at first glance, the kung fu wizard, is also the most self-policing since it means you're running out of a finite resource more quickly. Anyway these have to be discovered or learned during play and you can never have more than your Wisdom bonus.
If anybody can learn these secrets what about the monk? Well, most people can throw a dagger, too, it's just some classes are always going to hit with it more (fighter) or do more damage (thief/rogue). So on any given turn the monk may choose ANY of these to do twice and forget that Wisdom bonus jazz. The monk doesn't suffer tohit penalties for unarmed or improvised weapons and always does a minimum of their HD + Wisdom bonus in unarmed/improvised damage; that is, a level 10 monk does 9+Wis damage unarmed. They can also use any weapon that the player can show the DM a picture of Gordon Liu using but using a weapon that does more than d4 prevents you from taking a kung fu option that round. They also use their HD as a bonus to AC, so a level 4 monk with Dexterity 13 has AC 4/15 (17 for LotFP). Finally, all their unarmed strikes ignore all magical resistance.
I don't know how you would weight things for later editions, that's not my problem I sleep now.
Checks: DM discretion; otherwise normal action/in-initiative economy; monsters and other adversaries can also know all this kung fu in addition to their normal special abilities; normal rate of advancement.
Advantages: lets you lay a patina of kung fu boogery across an entire world really quickly by just letting every character or even every NPC have one of these at level 1, maybe grouped according to race or nation even; allows for more options in and out of combat without presenting so many options as to slow things down; focuses on core mechanics rather than if-then statements re: tack-on effects; greater versatility with weapon choices using the kind of simple common sense rule you aren't legally permitted to print in the PHB; can basically assign techniques and character flavor as treasure; built in quest lines.
Disadvantages: monk's starting damage output and maximum damage output are probably affected in the name of simplicity; loss of the more super crazy magic effects as specific "power" line-items in favor of doubling up on skill checks may disappoint some; in general while making the whole world kung-fu-y is easy, in a more traditional westernish fantasy setting the monk would feel somewhat less distinctly East-Asian.
Methods of augmentation might include: letting them wear armor OR benefit from their HD AC bonus but not both; letting them defeat an opponent with greater HD in single combat and in doing so learn their kung fu, like Mega Man; basing this stuff more on wrestlers or luchadores and tying all bonuses to Strength or Charisma.
The important distinction here is that, sure, a first level monk might not do as much unarmed damage in a round as they might with other first level monks, but the damage potential is still there; however, what they can do is take an improvised weapon like an autumn leaf and use it like a throwing dart, like Chinese Bullseye.
Meanwhile, as a general kung fu system this does not duplicate too many abilities found in other classes, or ones that are only unlocked at higher levels. The biggest overlaps would be with thieves who honestly need a lot of kung fu and could do with the added edge at higher levels. It messes with action economy a little but it also gives the players a resource (like ammo or spell slots) that they can LOSE: all you need to do is decide that one of the 900 types of boring undead gives someone chi blockage that characters have to meditate to clear and suddenly they have to worry about you taking away a new toy. Fight strategies get altered. This is Fun.
It's also something that potentially lets every class (and the monk) do the thing that defines their class more often.
Alternate Kung Fu for Feng Shui
The shotgun-cocking rule (add 1 shot to your Guns attack using a shotgun to go CH-CHAK, gain 1 extra damage) gets modified for martial arts: scream out the name of your move when you execute it, add 1 shot, and gain +1 to your Result.
In the tradition of Jackie Chan (or more specifically the Jackie Chan cartoon show) you may attempt to use Martial Arts in place of any requested skill and in lieu of making an Untrained roll; however, if you fail you look utterly, utterly foolish and cannot use Martial Arts in this way for the rest of the session. (Example would be using your chi mastery to tell if someone is lying instead of using Police but if you fuck it up you look like a big old Phoenix Wright idiot and you have to wait in the car while the big girls talk.)
Characters with Guns are equally adept at using them as melee weapons, though they all act as basically clubs.
When not using a Signature Weapon that is a melee weapon to hit an opponent you may elect to spend 1 extra shot and have your weapon break and become useless in order to add an extra 1d6 to your outcome, throwing the useless chunk away dramatically. Another character can use the broken pieces to any positive effect they are capable of but you never can.
All Archetypes may elect to fight in a Signature Look, a specific style or costume they either always dress as or in which they suit up when Shit Gets Real. The one rule is that the Look must be at least slightly incongruous for most situations, like the robes of a Shaolin Monk, the mask of a Deadly Venom, Ron Perlman's suit and boots from Pacific Rim, or the Chicago Bulls mascot outfit. Something that makes you super obvious. Characters sporting a Look get -1 to all attempts to pass undetected but are +1 to all attempts to find and exploit Contacts for information. Characters sporting a Look are also +1 Defense until the first time they take damage in a session, at which point that bonus is lost until they are able to safely make repairs or the following session (whichever is longer).
Finally, your Signature Weapon may be something you invented or something which only you CAN use as a weapon, in which case even when a bad guy has taken it from you they cannot use it against you. However, in this instance you lose the other normal bonuses from Signature Weapon.
Checks: All the other cooler and frankly more powerful things you can do in the game; most other characters still being better than you in whatever skill you're rolling; bad guys finding you easier; trading a needed resource for a temporary gain.
Advantages: Makes things work in most respects more like a Shaw Brothers movie, which is good because even in the new game the ratio of Run Run Shaw to John Woo skews a bit heavy in the doves direction.
Disadvantages: At its heart Feng Shui is a dirt simple game that gets clogged with sporadic granularity and this could be read as basically that exact thing; mechanizes things players should all basically be doing anyway if they're really in the spirit of the thing.
Methods of augmentation might include: just using one of these m'man? Figure it out.
I've used the "shout out your move" rule a lot and it works fine except that since it's usually used on Mooks its full effect is not often realized. The rest of this stuff is all really cosmetic overlay apart from the dramatic-weapon-break rule, which is adapted from my Mutant Future game.