I've been giving some thought to a signature ability for the Wudang techniques, but first, some research.
The Wudang in question is the fictional Wudang school/sect located in the Wudang Mountains, based on the real Taoist temples there, which are associated with
neidan or internal alchemy. In my lay understanding, this would be covered by RBRB's Internal Arts (
neigong). I'm sure there's some philosophical nuance based around Taoist vs Buddhist belief, but that's beyond the scope of the game and this exercise.
Back to the film, the only time Li Mu Bai is shown using Internal Arts is at the end of the film when he's purging Jen of the drug Jade Fox used on her (RBRB:
Healing Hands of the Mercy Goddess), and slowing his own cardiac rhythm to delay his own death from poisoning (RBRB:
Awakening the Golden Lantern I). However, he's shown to outclass everyone in the fights he's involved in suggesting mastery of External Arts, and his ability to balance on the tips of a bamboo branch even when Jen is actively shaking it with her whole weight suggests mastery of Lightness Arts.
Does that mean, in RBRB terms, he's maxed all 3 Martial Arts the standard way? Maybe. But what if this is due to a Wudang technique giving him a shortcut? And so I present my initial idea:
Wudang Technique I
You have attained such mastery over self that you are able to use your Internal Martial Arts to empower your other Martial Arts. When you make a skill roll using External Martial Arts or Lightness Martial Arts, you may use your ranks in Internal Martial Arts as a substitute.
I quickly realised that this technique doesn't quite match what we see in the film. If Li Mu Bai's Internal Arts were so good that he was substituting his External and Lightness Arts with it, then the depiction of his Internal Arts should be on par with his External and Lightness Arts, but the fact he succumbs to the poison suggests it's not. Which brings me to the next iteration:
Wudang Technique II
You have attained such mastery over self that you are able to use your Internal Martial Arts to empower your other Martial Arts. When you make a skill roll using External Martial Arts or Lightness Martial Arts, you may add your ranks in Internal Martial Arts to the roll.
This revision means that with even a single rank in either External or Lightness Arts, each will always be better than Internal Arts when paired with this technique. That better reflects what we see of Li Mu Bai's skill.
Now the question is how to pair this with Green Destiny. I will need to meditate on it and hope I don't experience Fire Deviation.