Somehow the idea of quadrupling the number of footguns is not as appealing an idea to some C programmers as you may think it is.

In general I think the appeal of "a better C" is limited. The value of C is that it's simple limited thing and there's a compiler for every platform. Your "Better-C" won't have that. What seems like the most universally acknowledged problem with C (unexpected cases of UB) also largely stems from this. There's some effort in the newer standards to nail down some of this in exchange for dropping support for some of the oddball historical stuff like not assuming twos-complement or whatever. Probably the correct path to a better C, rather than adding things on top.

Separate are the efforts at creating new lean systems programming languages that enable you to do the same things as C. But there's not much point in trying to extend C itself at that point.