There is certainly is no harm having a fusible link there. Especially if, like on some cars, the batt is on one side of the engine bay and alternator on the other (ie a long wire with more opportunity for chafing and grounding). I do not use a fusible link on that circuit since my alternator is only a few inches from the batt. The main issue is you would need to protect that wire on both ends since juice can run either from the batt or the alternator if the wire ever finds a ground (the battery should have priority since it can deliver hundreds of amps compared to the alternator). In short (now ain’t that funny) just be absolutely certain the charge wire is as secure from ground as possible.
