I think there is way too much paranoia here. The only motors that give no warning are the single cam V8s. The diesels will rattle quite some time before failing. The noise should be apparent to those paying attention; even over the diesel noise.
The real breakthrough in confidence comes with all the motors with ratcheting chain tentioners. 102/103/104, 601/602/603,606. I presume the 119 motors must have a ratcheting tentioner but we haven't done any failures on those motors yet.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician