Wrote a hybrid force controller a long time ago based on the Cartesian controller for the PR2:

https://github.com/gt-ros-pkg/hrl-pr2-behaviors/blob/master/hrl_pr2_force_ctrl/src/hybrid_force_controller.cpp

From what I remember, you should be able to send it a local direction cosines frame which allows you to decompose the Cartesian controller into control in the 3 linear dimensions and the 3 angular dimensions. For each dimension, you could pick whether it applies a target force using a PI controller or controls to a set point with individually specified impedance gains. Also does control in the null space.

It assumes a force torque sensor at the wrist, however.

Here's a simple Cartesian position controller I wrote about a year and a half ago:
https://github.com/gt-ros-pkg/ros_controllers/tree/cartesian-ctrl/cartesian_position_controller

This was designed to work with ros-control, but might have only worked with my fork of ros-control. This should let you set gains for each direction and possibly let you pick the orocos solver for inverse velocity.

I can't promise any support, but hopefully this code will point you in the right direction.

-Kelsey