I assume there is going to be some kind of test harness that allows developers to check their workflows.
By using WebAssembly, it's kinda by default fool proof. WebAssemby explicitly requires you to declare host calls inside your modules. If you try to use another host call that is not provided by flawless, your module can't be instantiated.
It's also important to notice that there are multiple standardisation efforts going on in the WebAssembly space. For example if you are using the rust `rand` crate and compiling to WebAssembly, it's using the WASI host functions for generating random numbers. While I'm waiting for wasi, wasi-http and others to be standardised, I expose my own interface for now.
Obviously, this also has a big downside. You can't compile all Rust code to WebAssembly. However, I prefer this reject by default approach, so that you are guaranteed to never have unintended side effects.
I'm a bit worried about the limitation of having to use the flawless namespace functions for everything.
So far, this looks more like a scripting runtime which uses Rust.