One of our developers, who has contributed extensively to the official WASM spec, wrote a library to create WASM gauges and standalone modules in MSFS (https://github.com/flybywiresim/msfs-rs/, under the MIT license). We are using it extensively for our WASM-based systems in the A32NX, and the unique features of the Rust language have proved extremely useful in development. We would love to see this get official integration so others are more inclined to make use of Rust and its memory-safe features.
Documentation: https://flybywiresim.github.io/msfs-rs/msfs/
Example of our systems code using Rust: https://github.com/flybywiresim/a32nx/tree/master/src/systems