defining the sizes of various numeric types (for example: "char" and "unsigned char" are 8 bits, "short" and "unsigned short" are 16-bits, ...);
C has addressed that with the sized types, like int_32t.
all this doesn't even need to be "the standard", but maybe could be a "standardized profile".
Yeah it would defeat the purpose of the whole C language to nail down all of those things, which are basically hardware details, as then the language couldn't be ported to other types of hardware. Having sub-standards /profiles for certain platforms, e.g. "C for x86" makes a bit more sense though