And then there is stronger braking to be considered, which almost always is some kind of disk brake which you can't do if there is no shaft to mount one on. Which means the spherical wheel system would have to be oversized to compensate for lack of such a shaft even if it would work to drive the car. Magnetic wheels have other interesting problems that would need to be solved such as when two cars get close to each other the wheels would start to attract or repulse depending on their orientation.

This is mostly likely not something that could be rolled out even in a concept car with present day technology unless there is some kind of trick that I'm not aware of. Halbach arrays are not without problems if you allow them to be unconstrained in all dimensions.