You can carry a medium format camera... That will give you way better tone and sharpness. Unless you're doing real street shooting, it's the best option if those are your goals.
For fast street shooting, those (superb tone and sharpness) are not a priority... The differences between a CV3.5 and a Leica2.8Asph when both are stopped down, prefocused and handheld, with ISO400 film, are close to nothing: everything in the image and all we do as photographers will matter a lot more than the lens... When a street photograph is great, no one thinks about image quality... It's not about that... Any decent lens is more than enough for B&W and color...
If you haven't owned one of them before, look for the smallest (shortest) 28mm lenses and give one of them a try... The R4M has uncluttered frame lines for 28mm, and with the CV3.5 without hood you are really unobtrusive... The whole set is incredibly flat! I can place it in my jeans pockets...
Size matters a lot IMO... Sometimes you won't be seen, but lots of times we are seen, and we better have a flat camera/lens set those times, to be able to get the shot, and even keep shooting around...
I carry a fast 40 and a fast 50 and a HexarAF too, for low light/difficult focusing situations, but I'd never add a millimeter to my 28 for getting more speed: I have never used it at 3.5 or 4 or 5.6 in my life! It's my most used lens just because of its size, and its image quality is a lot higher than I need for my photography.
If you have already owned a Bessa R4M with a CV 28 3.5, please ignore this well intentioned advice...
Cheers,
Juan