I currently use a few GT Omega ART cockpits.
I have been looking for something small that can be added to my existing cockpit frame, to provide "just enough" motion, for bumps and vibrations curbs etc... and then maybe a little more motion if it can.
I do not like the concept of the chair moving separately from the wheel... and would even prefer the monitor to be moving as well. Even though that is tricky to keep it from wobbling.
I saw videos of a simple 3 point system, with only 2 actuators, from PlaySeat that might be adaptable since the front end just rests on the actuators, while the back rests on a rocker-point, but never heard any more about it.
Cost is the biggest issue with these, some of them cost as much if not more than an actual race car.