Stick with your original plan. The FSDs make your plan superior to the trademotion kit, zhp shocks are bouncier than sport shocks, and a helluva lot worse than FSDs.
Those parts of autohauz, fcpgroton, rmeuropean, etc. sites are not always OEM, usually they are lower quality to aid in the cheaper price.
Having said that, if getbmwparts has a kit similar to ECSs (without the shocks/struts) I would use it, because recently some have had issues with ECS; getbmwparts has certainly earned their salt in the BMW community.
"All lies and jest, still a man hears what he wants to hear and disregards the rest."