You want to combine quantum computation with classical computation? Do you want them to run in parallel or in lockstep?

Also not all ciphers are Feistel networks, stream ciphers use Vernam construction and aren't reversible. This was used in an attack on USA export restriction which declared cryptographic hash functions as exportable, so it inadvertently applied only to Feistel ciphers, but a stream cipher constructed from hash function thus dodged export restriction, because stream ciphers are irreversible.