About non-setting specific martial arts supplements.
The short of it is: they either end up looking a lot like GURPS: Martial arts for 4th edition, or it's likely didn't do a good enough job.
The reason for that is, almost all martial arts are setting-specific (wrestling is the only exception I can think of). That's the often-overlooked truth, even something as minor as different styles of shoes can lead to profound changes. If people tend to wear leather or heavy cloth, attacks to the head become extremely important. Go south (shut up, you perverts-southern settings with lighter clothing), and you get much more finger attacks, pressure points and body shots. And these aren't even the most important factors.
Then we add the most common weapons and most common tactics you might encounter, and some styles end up being more in vogue, because they're lucky to have their weaknesses overlooked, or their strong parts are allowed to shine more often. Something as often overlooked as the size of the guard has HUGE influence on what defences one can use. With a katana, it's beating away more often than parrying in the fencing sense, because the tsuba doesn't protect your fingers nearly as much.
When some styles appear that solve most issues, the rest of the teachers try to emulate the successful ones, to find their own solutions to the same problems, or a mix of both. Or they go the "tradition/health" route. Or they go out of business (meaning not many people get to study it, even if they keep teaching it). That often means that if the situation changes, and an unpopular style would be a better fit, it often has to be re-invented anew.
Just some random thoughts on stuff I find lends flavour to an RPG combat. Sometimes, I'm thinking of expanding it into a supplement for some system and setting. At other times, I don't see the point, because who would be interested?