If you are using field weakening techniques to increase max. speed without crazy pack voltages, then the safe state is a 3-phase short across the entire motor. Otherwise in case of a control failure the back-emf voltage will become unlimited, go to a very high value (above pack), back-feed into the pack (through body diodes, or simply shorted FETs), possibly overcharging or destroying the pack.
You'd think a 3-way short on all phases at highway speeds will cause unlimited current, but that is in fact not the case due to inductance of the windings causing current phase lag, preventing the BEMF voltage from causing high currents (the actual maximum depends on specifics of the motor).
This really has to be designed as an entire system, the choice of using field weakening or not will directly define your battery pack voltage requirements, and therefore your motor control strategy, and therefore what kind of safety you need to add for contingency.
The addition of the fuses may make it safer, or it may also make it more dangerous, there is not enough information to make the call.