How do you migrate the old keys to a quantum fork without allowing the exploit to still exist retroactively? I could exploit the old blockchain, then migrate m

How do you migrate the old keys to a quantum fork without allowing the exploit to still exist retroactively? I could exploit the old blockchain, then migrate my stolen keys to the quantum blockchain. Forking doesn't work here. Traditional computing and Quantum computing are different enough that "porting" isn't just something you can do.