"Part of the problem is that he also wants to run the 135 rear brakes fully functional with ebrake." Correct
"there still is no reason to try to install 135 pumpkins in our car."
One good reason IMHO is the 4 holes Drive shaft, which is specific to the 125i/128i --> I don't think it exists any 215 diff with a 4 holes out flange that match with that Drive shaft.
...That is why in my original post i asked if it was possible to fit the Rear 135i drive shaft with front 125i one...
answer was NO so the best solution for me is to use the 335i/135i N54 AT Axles
