That implies that the suspension should go as low as 0.5 Hz to ensure isolation from building resonance.
I'm not so sure on this -- after all, at 0.5 Hz the relative stylus-to-record motion *should* be fairly well attenuated simply due to the fact that it's now several octaves below the basic cartridge/tonearm resonance, which is acting as a 12dB/oct high-pass filter.
From emperical evidence, the cartridge/tonearm resonance envelope definately affects the sensitivity of a boingy suspended turntable system to foot-falls and such. So I'm thinking that the primary suspension mechanism of importance is its Q, and flatness through its transition region . . . so it doesn't add any additional peaking to the tonearm/cartridge resonant peak . . . the exact rolloff point for the suspension simply needs to be a bit (an octave should easily do) below the that of the tonearm/cartridge. The best results will then be acheived because the slope of the attenuation (provided by both the suspension and tonearm/cartridge working together) is smoothly increased, without increasing the peaking, and the ultimate attenuation at very-low frequencies could be similar to the system you describe.
Another huge issue is how the suspension behaves with horizontal shock, in addition to its vertical behavior. I think that this is THE main flaw in the Linn/AR suspension, and just about every turntable suspension that uses compression springs. In these systems, since the mass of the subchassis sits above its support points, it's inherently unstable with regard to external horizontal motion. This fits with the long-time Linn recommendation of the Sound Org stand for floorstanding applications . . . something will minimise the addition of horizontal energy, yet cleanly transfers vertical energy to the turntable, where the suspension does its job the best.
Ideally, it seems that the subchassis should be underhung with respect to the fixed chassis, resulting in a stable, predictable horizontal resonance . . . and there's probably some perfect relationship between the horizontal and vertical resonant frequencies that would allow horizontal shock to be converted to vertical spring deflection (through pendulum action).