2010 R56s is looking like it needs new control arm bushings. I know officially its a whole process that requires dropping the subframe. But I've seen some videos where people remove the old bushing with a sawzall (to cut through the metal sleeve), and then use a wrench to get a Powerflex polyurethane bushing in. Has anyone done the later method? How easy is it for a novice? My biggest concern is accidentally cutting through the bracket.
Additionally, under what condition should I just replace the entire control arm?

EDIT:
A video I found of the procedure

 

I cant see why you would replace the entire control arm unless its damaged. Follow the advice the video gave and you'll be alright. Just dont go ham out with a sawzall and pay attention when cutting it. As far as the tool is concerned, a commenter on the video commented this:

• Just did this. I used 2- 1/2" floor flanges, 1- 5/8" x 12" stainless threaded rod, 2- 5/8" washers, and 3- 5/8" stainless hex nuts. I tried it first with a 1/2" threaded rod but stripped the threads before the first bushing pressed in. The 5/8" stainless rod had no problem pressing them in.

 

I did this in my R50. Easy job.

 

They're only $100 each for OEM replacements so I wasn't sure if its a "goes bad after x miles" thing so if you remove it you may as well just replace it. And good eye on the threaded bar diameter note. I'll make sure I grab 5/8's