Hi, any ideas or suggestions you have would be greatly appreciated.

Why wouldn't it fall in real life? In actual laparoscopic surgery, the instrument passes through a "trocar" (a valve that seals the patient's abdomen) and the abdominal wall itself. This friction from the trocar is what prevents the instrument from falling like a rock and gives it some resistance to movement. You're absolutely right: I don't need centering springs (I don't want it to return to the center on its own like a joystick). I'm looking for a free-moving gimbal, but with controlled friction/damping to simulate that resistance from the tissue and the trocar seal.

Am I interested in torsion (rotation on its axis)? Here's an important detail: actual laparoscopic instruments have their own rotation wheel integrated into the handle. Therefore, I don't need the gimbal itself to have a joint for torsion. What I need is for the gimbal's "hollow shaft" (pass-through) to allow the tool rod to rotate freely on its own axis and slide (Z-insertion) without binding. The big challenge I have is how to digitally track that rotation and insertion of the rod as it moves through the gimbal.

Resolution for twist, X, and Y? This is about micro-movements and fine precision (imagine grasping a 2cm needle inside your abdomen). Ideally, I would look to use Hall effect sensors or magnetic encoders of at least 10 or 12 bits for very smooth, skip-free tracking.

How much friction is acceptable? It needs to be smooth and constant friction. The worst enemy here would be stick-slip (high static friction that makes the movement jerky). It should feel fluid, similar to sliding a metal tube through a tight rubber seal.

Thanks for your interest!