And is a security nightmare. If I have an executeable, I have verified, I don't want the instructions to be altered in any way. In fact I prefer if it is impossible from a hardware level by marking them as executeable bits.
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.
You still need a debugging build, otherwise compiler optimizations will obscure the executeable to the point where debuggers cannot reliably debug it.