1: The theoretical Maximum of USB is around 60MB/s. Practically that is not often reached, usually USB sticks come around 30MB/s, which would be even slower than an SD card solution. Somebody would have to tell us how fast the USB controller is.
My Opinion is that USB would be awesome, because we could use cheap HDDs or SSDs. But I don't know whether it would work over USB at all.
2: No idea, if that is possible.
3: As far as I understand that is not possible. Processing the pictures to black and white would need the CPU to do that to 24 images per second! The CPU can not handle this.
Right now the CPU does nothing at all. All that the RAW feature does is simply writing the image "on" the Sensor directly to SD. So the CPU is in idle all the time.
4: Same as 3. This would require much more processing power.