That could be possible for browser apps which already have a sandbox. Doubtful for general purpose languages. For example I have a library and utility to change user password, or writing sudo alternative sudors etc. How would you even begin to sandbox that are core os utilities or need access to core os themselves.

more specifically, one can introduce policies into the runtime, or given rust hoist at least some of them into compiletime that would do things like (a) enforce syscall filtering based on crate or even function (b) support private memory regions for crates or finer grained entities that are only unlocked upon traversing a declared call-gate (c) the converse, where crates can only access memory they themselves have allocated except a whitelist of parameters (d) use even heavier calling conventions that rpc to entirely separate processes