But how is that different than what we have today? Windows for instance already does this for system files, and could be expanded to user installed files as well.
You still need a debugging build, otherwise compiler optimizations will obscure the executeable to the point where debuggers cannot reliably debug it.
Also, 3L runs in two modes: development or secure. In secure mode you can completely disable manipulation of source code (or strip it out) and mark all code as read only and have the system verify the code hasn't been modified when it is run.