but aside from some power efficiency gains, can’t I get most of the Mill’s advantages by simply using WebAssembly + WASI?
WASI looks like it trying to be a capability based design. Which is certainly possible on existing hardware, it’s just always been slow. The Mill ISA and security model should adapt quite well to WASI, and you might even have a micro kernel with paravitualized drivers that can run the API directly. Great effeciency, and scalability.