Yes, for sure my suggestion was an incomplete answer, but still you would want the lower language be GC-aware/GC-compatible so I am not sure what the advantages of having two languages would be compared to having a GC language that can have non-GC modules/functions.

We also have an example of something more similar to what you are asking with Javascript+wasm (or better Typescript+wasm). I think they are both a fertile ground for future growth.