If you like the sound of the Zephyr Mk III, there’s no reason to change the cant or stylus design. Just let Soundsmith rebuild it, as good or maybe better than new.
On the side, some people, including myself, are not keen on aluminum cantilevers. In this case, though, the cartridge seems to be tuned nicely to the line contact stylus / aluminum cant combo. I’m not sure other combinations would give you the same quality reproduction.