Sani sabik civilians may have a form of martial arts, the primary purpose of which would be fitness and basic hand to hand training, as the Blood Raiders (and other groups) draw from them for their recruits.
Even when not in the Blood Raiders or other paramilitary, the Sani Sabik also have numerous infiltrators and other agents, where unarmed combat skills would be important, for avoiding detection in the first place, and for escape/evasion. A person carrying a weapon is far more conspicuous.
There'd be an emphasis on observation, reading people to watch for muscles tensing, that sort of thing. As well as improvised weaponry. The correct way to use a chair as a weapon, without overextending and exposing you to counterattacks, etc.
But that goes for practically all military or paramilitary groups, Federal Intelligence, etc. It's not like there'd be unique special styles.
The Blood Raiders though, would have some of the better shipboard close quarters fighters. Zero-G, Zero-pressure combat training, that sort of thing. Again, much emphasis on observation, as they have to be able to seize a ship quickly, they don't have time to be fiddling about.
But most professional space troops would have such training anyway.
There is one group which I'd believe to be quite different, and that's the Sansha's Nation.
What their nature allows is not really a martial art, but it's all to do with their unique nature as a networked group.
Group combat. Each unit covering the vulnerable spots of the others. This provides an efficiency and effectiveness far greater than any other force could manage.