In fact, the 10W-60 oil choice was an attempt to mitigate rod bearing failures. BMW engineers know RPM based inertial loads are beyond the capabilities of lower viscosity oils. So a switch to a lower viscosity will not give a better result. However, the 10W-60 oils are not known for staying in grade properly, and the extended oil change intervals don't help that.
BMW's initial claim that bearing clearance was "too tight" is incorrect, has become a bit of internet legend, and was simply a way to attempt to address the problem. Increasing bearing clearance did NOTHING to improve the problem. The bearings are insufficient for the loads involved. Period, end of story. Higher viscosity and higher oil pressure are the only things that help a "too small" bearing live under high loads.
Also note, combustion loads are only part of the equation. Inertial loads at higher RPM far exceed combustion loads.
If the car is driven hard, the best solution seems to be preventative bearing changes at 50 or 60K miles, frequent oil changes and sufficient viscosity.
Edit to add that a gentle warm up is also a very good idea and seems to be part of the solution. Also, don't forget that cars driven gently tend not to have the bearing problems. There are plenty of examples with high miles and zero bearing issues.
Edit: For the bearings to be sufficient, they would have to be as much as 40% wider. Or reciprocating mass would have to be reduced.