If I may I'd like to offer a few comments about Naifanchi, Kyan and perhaps Isshinryu, which I've been studying for about 35 years.
Most of the karate reference books (such as John Sells work Unante I and II) list Naifanchi kata as one of Kyan's kata. But towards the end of 2005, Dan Smith (of the Seiubkan and originally a student of Shimabukuro Zenryo) explained that the source of much of that information came from is own lack of understanding. When he trained in Seibukan Naifanchi was one of their kata, and he assumed it came from Kyan Sensei, and never asked, but it's source was not Kyan, who did not teach the kata.
Another Okinawan stylist, Harri Davis, a student in the Joen Nakazato lineage, confirmed this. Nakazato also taught Naifanchi but it did not come from Kyan, but from a different instructor than the Seibukan source.
In face all of the Kyan descended groups, Matsubayshi from Nagamine, Isshinryu from Shimabuku Ezio, etc. include Naifanchi and all appear to have different sources.
Likely Kyan would have known the kata, even if only having seen it innumerable tims, but it was not part of his teaching. Yet all of his students who ended up teaching seem to have found it a source of value and included at least one of the 3 kata in their schools, perhaps as an Okinawan standard?
While there are 3 Naifanchi kata, in Isshinryu's case it is only an Isshinryu variation of the first one, Naifanchi sho-dan. The main difference is the kata begins stepping to the left, as opposed to most naifanchi/tekki versions that begin stepping to the right.
Isshinryu is not alone as there are several other groups that do the same. Isshinryu's source may have been Motobu Chokoi (or it may not have been). The Japanese video of his son's performance has the kata performed in both directions, which is not illogical as the kata mid point just reverses the beginning 1/2 of the kata.
Of course Isshinryu's version has other flourishes keeping with it's founders (Shimabuku Tatsuo's) vision, but the essence of Naifanchi remains.
The problem is most of this remaisn oral history. You can or cannot prove it from books or other internet discussions. But none of them constitute proof, especially as the true Okinawan tradition was NOT to document systems and history (a modern phenomena), and the truth was whatever your instructor told you.
As for the application potential of Naifanchi, that depends on what work you want to put into it, it can be nonexistent, standard or very deep indeed. Yes the technique could be used on the ground (as any kata's technique could be). Isshinryu's founder had specific teachings to counter the mount in his students study of 'kumite'. But personally as i've found little reason to concern myself with grounding in my studies and teachings, I don't consider Naifanchi in that light.
On the whole I see the first line analysis of Naifanchi as being:
1. conters for striking
2. counters for grappling with a huge range of lower body attacks in the stepping potential of the kata.
Pehaps this is helpfu,
pleasantly,