> such the submodules of a program cannot corrupt parts of memory that belong to others

IME you can eliminate tons of issues using language-based safety. That just wasn't possible before Rust without taking a perf hit. And you can still use vm in a unikernel for e.g. guard pages, read-only segments, demand paging etc.

I'd say the main advantage of the unikernel approach is the ability to be very intentional about where/how you introduce complexity. For a certain class of high-performance systems software, that has direct implications on reliability and performance.