When I did mine, I raised the front of the car with the bucket on a tractor and a couple chains, then placed GOOD jackstands under the chassis at the jacking points. Then I placed a jack under the pan (with a wood block against the pan) to hold the engine up. The motor mount bolts had Allen heads and were removed from below. Then I removed the brake calipers and hung them from the sides, as you thought you could do. Then, I removed the swaybar bolts, the shock top nuts and then the subframe bolts, with the tractor's bucket a little bit below the subframe and let it drop into the bucket and backed away from the car. It is easiest to use spring compressors on the springs so you can work on the subframe as an assembly while it's out. The old subframe bushings literally fell out of the subframe, so they were no problem to replace. On my car, I had to replace the subframe with one I got from a 114, so had to drill access holes in the replacement subframe for the motor mount to engine bolts. The mount to subframe bolt locations were the same. When I replaced the subframe in the car, I just put it in the tractor's front bucket, raised it up to the car and bolted it down. No problem at all! Sorry for not responding sooner, I was away for a week or two!
(edited to include the below comments) The picture you have posted shows what I think is an '86 - 89 subframe, as the upper control arms are solid instead of stamped, which is a nice improvement- they are supposed to be stronger. I raised my car a little higher than most people would since it was no effort to do so, so I ended up with the front about 4 feet off the ground, with the rear bumper almost touching the concrete. The engine support bracket looks like it would probably work fine, I welded up one somewhat similar to hold the engine up when I had to replace the transaxle in my sister's caddie, and it worked well. Another point is that I did the job over at my brother's "barn" (read 6500 sq ft shop) with almost every tool known to man onsite, including two metal lathes, milling machine, brake machine, valve machines, 2 hvac machines, distributor machine, tire machines, several 4 gas analysers, 4 post lift, etc ad nauseum. He has spent most of his life collecting cars and tools, so he has not one, not two, but SIX rollaways full of smaller tools. Believe me, it is NICE to have the right tool at your disposal.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C