My two cents. . .
BoseŽ Learning Center - Bose Suspension System
So yeah the idea with bose is you have a very fast EM-motor that allows it to expand and cotnract quickly and fluidly(not to mention dynamically).
If you could find a set of those it would be relatively simple. . .send a signal to expand or send a signal to contract. No leaking problems.
I saw this in PM a few years back. I think the reason it has not been developed is because the components are too long. They are about the same length as uncompressed springs. . .but they don't get much shorter once weight is applied. Causes the vehicle to ride too high.
<edit> which would not be a problem if you pick a chassis with the mounts high enough into the body to set the wheel wells just above the tires. If you were to build a chassis for these you could put the mounts very high on the frame as opposed to a few inches below.</edit>