Roller bearing crankshafts, another of those ideas that sound great, until:
1. they mention that the crank comes apart rather easily, sometimes in the middle of a trip
2. it increases the cost by a factor of 10
3. load capacity of roller vs. plain bearing: 6" mains and 4" rods would be a good start, it only worked because the engine turned low RPM and developed no power. Ask Enzo about roller cranks, but be walking away so he can't hit you
4. brain surgeon + many fixtures for assembly or service
5. rollers do not contain oil pressure, which means individual feeds from the pump to every journal, the crankcase looks like a subway line
6. very noisy, very difficult to diagnose problems

W. O. Bentley was respected as an engineer for his money.