Don't Forget HEMA Disciplines!
I practice Italian longsword, which is a Historic European Martial Art. (Commonly referred to as HEMA). I discourage the simple addition of "HEMA" to your list, because then you would need to lump together Karate, Judo, Aikido, Tae-Kwon-Do and Kung-Fu as "Asian Martial Arts." Sure, HEMA is less codified and practitioners usually study more than one system, but it covers such a large range of techniques, schools, and/or disciplines that it deserves the nuance.
Some HEMA disciplines could be: German Longsword, Italian Longsword, Spanish Greatsword, I-88 (Sword and Buckler), and English Quarterstaff. This does not work well, though, because German and Italian Longsword cover more than longswords; armored and unarmored combat, grappling (in armor or plain clothes), falchions, bucklers, and daggers are included in these martial arts. Alternatively, you could call each of these disciplines by other names: "German Longsword" can be referred to as the "Ringeck / Lichtenauer / Talhoffer Tradition", and the "Italian Longsword" could be called the "Fiore del Liberi Tradition." I've recently heard the argument that the Fiore's system should be called "European Longsword" because he very likely travelled around Europe to formulate the system he did. Even so, these are just named after some people who had their own widely known schools and may not have agreed to recognize the people we grouped them with as within their own discipline. So HEMA disciplines are maybe not as settled as you'd like them to be, leading your product to be not that great.
I know of HEMA clubs which don't have much in the way of hierarchy. I also know those who do have a ranking system are often not recognized by other HEMA clubs. While Europe had an expected progression for their warriors, (page -> man-at-arms -> knight) their "ranks" really meant more about what their job was and not how good or experienced they were at it or how they got there. So assigning strict "ranks" where there really are none is silly!
A Suggestion
Look at the SE "tag" system. Users can suggest tags of their own, but occasionally people sort and remove under-used tags. It's a decent system which takes advantage of the users' knowledge of the subject. The developers for this network of sites likely know little of each particular site, but gave the communities the tools to develop the tags and maintain them. We even have the occasional "burninate (delete) the '___' tag!" conversation in the meta sites for each SE site.
This means that an individual who studies a particular flavor of karate, Judo, Krav Maga, and their wacky personal discipline named "SickOfTheSuffix-Fu" can apply those tags to themselves. If asked what rank they are for each art, each practitioner can see a list of what others have already put in, and use those. Sure, you'll occasionally get something like a bare-knuckle boxer with the rank of "first generation greyscale unicorn pink bunny of the fifteenth class," but that's the life of a social network for you.
This approach could even use a simple SQL database to relate known disciplines with their ranks, and it's a simple matter to add, store, and recall ranks for disciplines. Even better, the users tell you what the rank system is!
