>I've been working on a related concept, but more along the lines of developing a low-level IR (LLIR) and corresponding syntax that allows direct coding in the LLIR. It would essentially be a portable assembly language. The LLIR could be then be compiled down to machine code for different architectures, or even run directly in a VM.

Isn't this WebAssembly ? Bonus points they have sexpression based format and a binary format and are working on a LLVM backend for it + a bunch of JIT integrations, making sure it's portable and have a lot of people working on it from multiple companies.