Platform with passive "weight-bearing" element to take some load off motors/actuators

I'm just starting to think about building a DIY motion platform, and I'd like to see if I can come up with an idea or two to incrementally improve on the great work that everyone here has already done. I'd like to do more than a 2DOF seat mover, but don't think I'll go all the way to a 6DOF Stewart platform for my first build.
One concept that's intriguing is some kind of passive weight-bearing element that can support most of the platform's weight, leaving the motors to primarily drive movement rather than holding up several hundred pounds of weight. The 2DOF seat movers have long leveraged this concept by placing the pivot (universal joint) at or near the center of gravity. Kinemaniacs/Ark Dynamics have a patent on a 6DOF Stewart platform that includes pneumatic cylinders bearing the weight, so they can get away with using smaller hoverboard motors. I haven't seen the concept applied to 3-4DOF systems although I might just not be familiar with all of the work people have done.
It seems like a good idea, but maybe I'm missing something... are there any disadvantages to adding a weight-bearing element to a platform, to reduce the load on motors? Obviously cost could be a factor, but it seems plausible that the added cost could be offset by being able to use smaller/cheaper motors. (Or better performance from the same motors)

That's a clever solution. It seems to me that with the right spring rate (perhaps by using an adjustable-rate spring), this could actually make the motion feel more authentic since it would mimic a car's suspension.
As a variation of your idea, I've seen some people put their entire rig on springs to get better effects out of a bass shaker. Maybe one of those springs, with the