If the attachment points are the same...don't see a reason why a brembo and ST ring couldn't be interchanged.
This is the reason why I went with my UUC/Wilwood kit...parts are a lot cheaper since it uses the OEM M3 rotor and a fairly common pad...as long as you stick with the 4pot calipers. 6 pot? Pad selection is a whole different story.
But, I think the Brembo and ST stuff will last a lot longer than OEM parts since they are bigger and thicker, can dissipate more heat faster, and made to handle more heat. While replacement parts are expensive, I think you get a lot more mileage/track time out of them. Not saying the a BBK is always cheaper in the long run...