Cool that you are actually going to do this! I guess having DSC as well makes it hugely more complicated. I think in that case you also need the steering angle sensor and yaw sensor, but the most difficult thing I would expect it for the DSC controller to regulate the throttle/power. If you have drive-by-wire that would be the first step in solving that I suppose.

Since my first post I looked into it a bit more and found a very useful Facebook group called "MK60e5 and MK60 ABS retrofit group" with a lot of information. It seems that there are 3 versions of the Teves system that are interesting:
MK60 - from an E46
MK60e1 - from a 4 cylinder E9x
MK60e5 - from a 6 cylinder E9x
These systems should all have a 4 channel system, but from what I've read the MK60e5 system regulates the rear brake pressure really individually, where the other two regulate it to the wheel that starts to slip first.

I actually had a 4 cylinder E90 myself and now have a 6 cylinder E90. The wheel sensors on those systems are not the same, the 4 cylinder uses a toothed ring with I believe a passive sensor, but the 6 cylinder uses something like a magnetic ring that is fitted inside the wheel bearing together with an active sensor. I think I read that the ABS computer can be configured to work with either of the 2 sensor types, but I'm not completely sure.

I was wondering whether the BMW sensors would not simply pick up the signal from the tooth rings on the Cosworth. The amount of teeth might be different, but I would expect that shouldn't really make a difference in generating a useful signal.