OCaml - Rust interop would be very cool, whatever low-level stuff you can throw into Rust while being able to use it from OCaml would be interesting.
[1]: https://github.com/zshipko/ocaml-rs [2]: https://github.com/tezedge/ocaml-interop
[1]: https://github.com/zshipko/ocaml-rs
[2]: https://github.com/o1-labs/proof-systems/tree/a4b06e71106704...