hmm, this looks like a project for it self...
And - yes it sounds like lot of fun.
But in fact I was hoping just for two old versions of Rust. One for XP, one for NT, or 2K.
If I have to cross-compile Rust, this project becomes to time-insensitive.
As far as I know there was never a version of the Rust compiler that could run on Windows XP. The compiler uses APIs for things like symbolic links and locks that don't exist in XP and earlier, and it’s been a long time since LLVM supported running on XP.
For a while you could carefully compile some Rust code for XP, but that stopped working and was removed after Firefox no longer supported running on XP.