Just a FlashFixed flasher. Unless he's downgrading a 800A to a 720A, there is no need for firmware/crossflash patching.
the dru500a isn't made by liteon and not supported by omnipatcher. ask the codeguys, maybe they can patch the firmware for you.
Downgrading firmwares to older versions never require firmware patches no matter which manufacturer's drive you're working with. AFAIK, the downgrade prevention for drives by any manufacturer is always implemented in the firmware flasher, not the firmware. OmniPatcher is a firmware patcher and never ever touches the flasher (well, starting in 1.4.3, it never touches the flasher; it used to before that).
Does the 500A flasher even have a downgrade check? I think there are flasher-patched versions of the 500A floating around somewhere, but all the information regarding that is somewhere in the rpc1.org forums.
Finally, I don't quite understand the question that you're asking. You're asking about downgrading firmware and about adding more media support. Adding more media support involves upgrading the firmware. Downgrading a firmware to an earlier version will never ever add any media support and will generally reduce your media support.