In case anyone here is interested in Rust, it's now very easy to use BLIS as a BLAS implementation. This in Cargo.toml is sufficient (the BLIS library will be built internally, or you can use the "system" feature to pick up a system-wide installation):
[dependencies]
blas-src = { version = "0.7", features = ["blis"] }
https://github.com/blas-lapack-rs/blis-src
https://blas-lapack-rs.github.io/usage
Among others, it can be used by ndarray (
https://docs.rs/ndarray), which plays a similar role to NumPy.
A high-level linear algebra interface with mixed-domain/mixed-precision support has yet to be written, but would be a great project.