Sorry but you are wrong and that is your opinion. People buy a CINEMA camera and then want to use clinical oversharp lens and they result in a 'video look' is pretty pointless!
Before righting off all C mount lenses, I'd suggest you listen to what others are experiencing in a positive light. I can certainly vouch that the several HIGH QUALITY C Mount zooms used on 16mm and Super 16mm cameras in the past even surpass old B4 ENG lenses.
Also pretty pointless is your suggestion of using FULL FRAME with a 3X crop lenses for the BMPC! The M4/3 Speedbooster or any of it's cheap chinese contemporaries at this time do not exist for purchase. Some of the C mount lenses have as much fine glass and elements in them as much as the "decent 1960's-1980's MF lenses from Zeiss, Nikkor, Olympus, Canon." you suggest as many were made by them!