I know it'll sound like I'm just coming at the same thing from the other side, but the purpose of the mass damper was not to allow for more compliant suspension, but to stabilize the aero platform.

And the way the regs were written at the time, "any specific part ofthe car influencing its aerodynamic performance must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom)," and "must remain immobile in relation to the sprung part of the car".

The regulators fully understood its benefit–as did McLaren, Ferrari, Toro Rosso, Honda, and Midland, who were all testing their own versions of that system–but it's hard to see how a moving weight strapped to the sprung part of the car in order to improve the aero platform is anything but illegal.