There are some good points here, and a few absolutely ridiculous assumptions mixed in. Equating a 12 Volt DC wiring system to a 120/240 volt AC house wiring setup is comparing apples and oranges. It's not uncommon for a 12 volt starter to draw 300 amps or more- - - - -that's why 12 volt battery cables are at least 4 gauge.
So far as the safety of a source circuit for a fuse block or other accessories, do what the manufacturers do, and wire in a fusible link to several circuits. They come in various gauges and current capacities, and the circuit protection can be tailored to the load. The only circuit where an automatic-resetting breaker would be appropriate would be headlights. Even with a serious short, the lights need to flash on occasionally for safety.
A high-output alternator can supply 100 amps or more to the battery immediately after starting, so pegging a 25-amp ammeter is not only possible, it's very likely, even if the accessories are wired to the downstream side of the meter. Shunt the heavy charge current enough to keep from damaging the meter, if you want to keep the dash looking original.
Jerry
