I have been thinking of a controller like this, which would be pretty fun to use for space games.
The ellipsoid marked as "Hand Piece", is supposed to be braced to the frame with motion encoders and need to push back the Hand Piece to the 0 position in case the user stops adding force in any direction.
Additionally, the hand piece can also have 5 buttons, 2 placed for the thumb and 3 placed for the 3 longer fingers each, with the button for the middle finger being a scroll wheel.
This should make up for actions like, Primary and Secondary fire, Target lock and cruise control adjustment, hence freeing the second hand for controlling utilities on the keyboard, or eating snacks. Whichever you prefer.
Your reply is helping me shape my ideas better.
If I were to use other objects as reference, it would be a 3DConnexion Space Mouse, shaped more like a handle to be held horizontally, and having extra buttons and a scroll wheel, right on the handle instead of around it.
The reason I went into making a frame was because I doubted being able to make something having a low movement actuator with those many axes and yes, I started looking into having linear actuators for the thrust controls. But if there is already a product as the Space mouse, then most of the engineering has already been done and all we need to do is, change the packaging parameters a bit, provided the 6 DoF actuator is available as a component. Also, the user won't have as much arm fatigue in this case.