My idea is to create a Cartesian spring-damper system. Since there is no generic 6-DoF joint with stiffness and damping, I tried to proceed as follows:

Three prismatic joints (x,y,z) in a row, followed by three rotational joints in a row (rz, ry, rx). Since there needs to be a link in-between two joints, I added dummy links between each pair of joints.

The issue is that these dummy links need to have a non-zero mass and thus distort the desired behavior. I assume that extremely small dummy masses might be an unwise thing to do.

Does anyone know of a solution that doesn't require a link between two joints?. Could a behavior like this be implemented in a plugin without extensive efforts? Are there alternative promising approaches to my problem setting?