I definitely agree with all your criticisms of the memory semantics in C, and I would love a language that fixed these flaws, but the "ideal" low-level language

I definitely agree with all your criticisms of the memory semantics in C, and I would love a language that fixed these flaws, but the "ideal" low-level language is still a lot closer to C than it is to anything else. I also think that C, being low-level, is much better poised to deal with experimental ISA designs than higher-level languages. For instance, one mechanism of manual cache control could be that you set bit 63 in a pointer to indicate that loads/stores from should place the corresponding cacheline in a high-priority. That's pretty trivial with a pointer in C, but a lot harder with say a C++ reference.