A rewrite of such technologies would not fix their semantic problems and related architecture decisions around tractability, debugging etc. For example, rewriting LLVM and GCC does not fix the underlying problem of missing code semantics leading to miscompilations around provenance optimizations in the backend. Likewise, Vulkan is not an ideal driver API (to argue on GPU performance) and let's not even start with OpenGL. POSIX is neither optimal, nor has it a formal model for process creation (security). So far there is no good one for non-micro Kernels.

From my experience with C++ I do expect 1. "verschlimmbessern"/aggravate-improving due to missing edge cases, 2. only spatial problems aka bound-checks to be usable (because temporal ones are not even theoretically discussed) and 3. even higher language complexity with slower compile times by front-end (unless C++ v2 like what Herb is doing becomes available).