I'm curious why you perceive SBC as being "very problematic." When it was first introduced in 2003 many customers brought their cars in because it was different, and made noises which they were not accustomed to. Actual problems seem to be reasonably rare.

Similarly, why do you percieve the OM642 as unproven? Mercedes replaced the OM647 (5 inline) and OM648 with variants of the OM642 in 2006 and it remains in production today - longer than the engines it replaced. It's been used in consumer and commercial vehicles around the world for 7+ years. If there were problems, don't you think they would come to light by now?

Edit: you're right about 211 ball joints, they seem to be a bit on the short lived side. On the other hand, a ball joint gives plenty of notice when needs to be replaced, and neither the part not the labor is all that expensive.