I think the fundamental issue is that the MPS6 was never designed as a track car. It is a "light luxury GT", a genuine 4 door high speed in comfort touring car. Rather than thinking of the suspension as being a somehow deficient aspect, consider it as being entirely suited (within price limits) to the job it was designed to do. If you want to take an MPS6 around a track the first thing you'd do is strip it out to reduce weight, rather than stress (initially) about suspension issues. I think it's a it of a shame to flog an MPS around a track actually, unless it is specifically rebuilt for the task, in which case it is largely written off as a road car, which would be another pity anyway. That's just my opinion and I know others will feel differently.
CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18