I finally came around to finishing my blog post about all the steps I to go through to use Rust in your C++ Bela project. There were quite a few snags for me to get through initially as I had never done anything like it. Once I set it up, however, it's been zero problems. I thought I'd summaries it all to make it easier for anyone else to jump in:
The reason I didn't use one of the existing Rust bela crates was that I didn't want to port the libraries for interfacing with I2C devices I'm using to Rust. Adding Rust to the existing C++ project seemed easier, and doesn't seem to have had any negative performance implications.
@l0calh05t: I added the compilation options you listed in your recent and similar blog post, hope you don't mind.