The general feeling should be these characters move in unnatural ways. A very cool feature/power for example was Skate: unnaturally sliding without friction on surfaces. Mechanics-wise, psionic warrior types should be able to do stuff such as very short range teleports to represent extreme sprints (psionic charge), like Zealots in Starcraft 2, or Spider Climb for part of the movement, short flights etc. Very high mobility, like the Monk in a way, but more supernatural.
Attacks-wise, there were many peculiar things. Psychic blades of course, but also far weirder stuff like melding of physical weapons with the body, making their arm become a blade. Also a lot of Smite-like abilities, where the weapon is charged with psychic energy, dealing extra Force damage, pushing the target away etc.
Basically they should be more mobile than Monk but less able to do multiple attacks, and have their attacks have the nova potential of the Paladin, but with less damage and more additional effects, especially forcing movement.
Of course, if it would be a class instead of a subclaas, then you could have subclasses going for more control, more defense of allies, more attack etc. As a subclass you have to limit all of this, or create a huge subclass with a power list or perhaps a near-copy of the Battlemaster, with different, psionic maneuvers, which would feel more supernatural but also leas universally useful than the Battlemaster. For example no goading, no disarming, no precision, no rally, but better "Intercept" (like the maneuver on the new Class Feature Variants UA, but with range and maybe less stopping power), strange movement attached to the attack (in a "before or after" fashion) and the possibility of damaging yourself to pump up the attacks, representing the strain in applying psychic power.
The key is, like for the Psion, a lot of flexibility and "sacrifice X to improve Y", but inability to take unrelated powers. For example this "Battlemind" Fighter could take maneuvers only in predefined bundles or skill trees, so that you can't be both very mobile and very damaging or very protective.