Maybe install two cameras, one each side of rear window at drivers eye level. Blind spot solved. Have to read the law for sure.
It'd never be legal. You would be looking at a camera on the dash, not looking to either side of you, so no matter what you did and where you placed it it would be very unsafe.
And, you say that having those 2 cameras there would solve the blind spot, not really. The blindspot is when a car is almost directly next to you, but not quite so you cant see them unless you turn your head, so the blindspot would be even worse with the cameras.
Don't want to bash your idea or anything, but it'd never work. And, IMO, trucks would look bad without the mirrors