I am currently opting to re-cone any blown field-coil speakers. A good craftsman can make a full kit from parts as they are still available.
I have thought about NOS Alnico replacements, and if I were to do it, I would use only a choke as a replacement for the field coil in the power supply. Another idea would be to remove the coil from the basket, if the situation was a total loss, and still use the same exact choke. I have never had a bad field coil yet- only voice coils, surrounds, cones, spiders, etc.