I don't remember reading about you doing the front M3 suspension, but even if you stay non M fitament up front I'm pretty sure you can get the M3 front stingray underpan and M3 FCAB carriers with non-M bushings. It should all bolt right up to your front suspension and create more structural ridgity replacing that tubular triangle in your picture on page 1. That or even get the non-M stingray pan.
If your front control arms are loose replace those and do the inner and outer tierods. Could do the steering guibo too.