I think this is a noble pursuit, please keep us informed on you progress. Figuring out how the make a replaceable BJ on the control arms would save fanatics tonnes of $$
I've been eying e36 ball joints as well as a possible press in for the xi control arm. I think there is a Mercedes BJ thay may also work. I've two sets of old arms I was considering experimenting with. The outer ball joint casing is really pressed in hard. I've tried using a cold chisel to pry the casing out but it will not budge. It may have to be cut out. The xi outer ball joint is surrounded by a rubber damping sleeve which in turn is captured by the outer casing and a bottom cap. Do the e36 balls have a rubber sleeve surrounding the BJ.