A possible path would be something initially running on an SBC, like a RISC-V board or even an FPGA. People buy these boards to experiment and use for simple tasks. Something really interesting could gain a small initial following and slowly grow from there.
It does not have to be completely isolated. You can still have support for some common communication protocols and maybe some client software running on a mainstream system to do various things.
I'd like to see a minimalist os that just runs multiple instances of wasm micro or maybe wasmer. It would only have to support the wasi. A scheduler, time support, a sockets implementation and a file system. Targeting a sbc makes a lot of sense for that.
It does not have to be completely isolated. You can still have support for some common communication protocols and maybe some client software running on a mainstream system to do various things.