You fuse a cable at the supply end to protect the size of cable, Anderson plugs are safe, which is why they were designed for fork lift batteries. Beware of cheap isolators as they can cause high resistance. An Anderson plug is an isolator in its own right.Nice system @Glenn Board and I can see why an electric winch is preferable.
On your proposed use of isolator switch and Anderson plug I would consider carefully putting a fuse between them lower than max rating on the Anderson plug. However, I'm not an auto electrician, just cautious about overloading electrics.