Well, I'm looking at the picture of the stud that holds the subframe in place and I'm not sure that you can do the install on the vehicle. It would entail removing the stud, so as to be able to pass a threaded rod through the bushing, but I'm not sure how you would get the stud back in, without dropping the subframe.
Here's a link to a commercially available tool, which may give you some ideas:
http://youtu.be/WCIlYkttQ2s Also, as you search the web for info, you'll want to look at what the e30 guys are doing, as the 318ti rear suspension is very similar to the e30.
By the way, that's a common ball joint puller that most of the guys are using, an autostore commodity that they just grind down to fit openings in the bushing flange.
Paul