I don't see what the issue with having a high amperage breaker for the winch? Surely the winch will have a designed max amperage draw, you would size your breaker appropriately for the load.
I considered this. It’s pretty hard to find a 650A breaker, and anything remotely close gets expensive. Fuses are quite a bit less but then you have to carry spare fusible links, just in case. A battery kill switch is kind of a middle of the road solution - it won’t stop an over current situation but it can prevent them when the winch isn’t in use.