Julian,
The issue is breaking the B+ to battery line with the alt energised and spinning. This iis why I am not advocating using a fuse. The LR fusible link, mounted in a suitable housing, would be a much better deterent to this than any type of push in/pull out fuse.
If you refer to your wiring diagram in the original post, they are three sets of (fixed) coils providing the output current/voltage for the alternator. They are arranged similarly to a 3 phase power unit. Following them is three pairs of diodes to convert the 3 phase variable frequency (with RPM) AC from the coils to DC voltage. The diodes are a high frequency capable type, not mains frequency units.
To control the DC voltage, the regulator adjusts the current in rotating exciter coil. (Voltage is a function of frequency and strength of the rotating feild which is in turn dependant on the exciting current).
Think for a moment of a bog standard coil ignition system. A current flows through the coil primary, increasing from zero until it reaches a constant level when the coil is magnetically saturated. This means that the coil is storing the maximum amount of magnetic energy that it can.
At some time after this, and timed carefully to the needs of the engine, the points open and stop the current flow. The result of this is a very rapid collapse of the magnetic field in the core, producing a high voltage pulse in the output of the coil, which then fires the spark plug.
Now, in the case of the alternator, if the alt is excited (field energised) and running, open circuiting the load terminal by blowing or removing a fuse, will create a pulse of substantial voltage, in a similar way to the ignition system but in hundreds rather than thousands of volts. This pulse will exceed the reverse voltage (blocking) capacity of the diodes and destroy them, most likely producing a short circuit and burning out the output coils of the alternator within a very short period ( 10 secs).
Hence the link must be of a type that is replacable but not subject to mans interference. Hence my reccommendation of the Land Rover type you suggested.