assign format version 800
Yes. To be clear, my technology knows about the 1.32 format change for the SD assets, and will automatically format the model differently (even though they both have .MDX extension) based on whether the model header says version 1000 or version 800. So if you open a version 1000 (patch 1.32) model, and then you simply change version to 800, when you save, my subsystem for writing the model binary to the .MDX file will change the format to match.
The only format difference is Reforged metadata that leaked into the format anyway because Blizzard was in a hurry while developing Reforged. Because of this, although there is enough different to break the model in the old software, there is not actually any substantial differences between the meaningful-ness of the model contents. The difference is mostly in the MATS/LAYS chunks, where there is fresnel and emissive color information and other Reforged HD data that always has zero values on SD models. The reason the model fails to load in old software is the data alignment problem -- the old software does not know to skip over the irrelevant crap because the format uses binary fixed offsets to read the information.
Edit 2: The format version numbering is a dumpsterfire by the way. Someone once sent me a leaked copy of World of Warcraft Alpha. It was -- like Reforged -- a derivative of the Warcraft III engine and so it also used the .MDX extension and the version number was also increased up to 1000 and above on that. But the format was different. You can read about how to parse the FormatVersions above 800 in the previous time these numbers increased in the 2005 versions for World of Warcraft, but because there is no discernible difference in header version information
between a WoW MDX version 1000 file from back then, and a Reforged MDX version 1000 from 2019+, the only way to detect which format I was seeing would be grotesque guess and check with the binary fixed with offsets -- or maybe it is impossible. (Actually, maybe we could scan the file for chunk tags because WoW MDX 1000+ uses BIDX and BWGT for bone indices and weights, whereas Reforged MDX 1000 uses the tag name SKIN)
So, my software will still break and crash if you are a blizzard employee with a copy of World of Warcraft Alpha from 2005 with MDX version 1000 models from that era. The MDX version numbers counted up twice because even at Blizzard (I assume, having not been there) these kinds of technologies are not so well documented. The good news is that around the time WoW released, it stopped using this format, so I don't support the World of Warcraft MDX format at all since that would be an incredible technological effort -- maybe impossible without the files -- and the result would be pointless since almost nobody has those.