What if this occurred? Would not a fuse at the battery be appropriate
That would be the same as the stud on your starter relay coming loose. It's not fused either. It comes down to the length of wire from the battery. Is the extra 36" a risk? If you consider it a probable cause of a fault, fuse it. It's like the priest's holy water. Might not help, but it won't hurt. IMO, the wire to your starter is much more likely to be the source of a problem. It regularly carries VERY high current and comes close to your exhaust manifold/hedder, is unprotected, and large enough gauge wire to really carry some serious fault current.