I'd like to suggest a possible enhancement: spin.
When you shoot another mote and hit it off-center, it should pick up spin, and impart more of the momentum to spin and less to movement. If you hit the mote nearer to its center then the shot would impart more movement and less spin. When a mote bounces off a wall the spin would have an effect on the bounce. And maybe if a mote is spinning, its path would curve?
For your own mote, the shot always comes from the center, so therefore shooting would not impart spin to your own mote. However, when your mote bounces off a wall that would impart spin.
I could see this idea having an effect on impasse levels.