I don't know enough yet about programming for 9P as a target but it looks like that project is in Rust. So, effectively, you'd need to both ensure that you can compile for that platform (extending rustc and/or llvm may be necessary) and ensure that any system calls that don't match up are worked around. The author states that they're not working on any new features but may merge them so, it might be a good project for someone to take on from multiple perspectives (compiler writing, low-level system arch, etc).