Does it sound enough "single coil"? It still has two coils albeit with different local sensitivities. Higher Gauss at the tops of the rails will reduce effective aperture lenght and thus improve high frequency response, though I am not sure if this has much effect in a bass where the wavelengths of harmonics are relatively long.
I would use small stacks of thin insulated transformer laminations (silicon steel) for the blades. These conduct flux better than low carbon steel and reduce eddy current losses.
What do you want to improve?