Comment by RodgerTheGreat

You're describing a hypothetical piece of software that would be easily two or three orders of magnitude more complex than the current Forth, and potentially be entirely unfeasible to run on a resource-constrained 8-bit system. Self-hosting isn't a cute trick, either- it's a functional requirement.

Forth makes bootstrapping and cross-compilation a straightforward exercise. C provides no help whatsoever until you've climbed to the top of a mountain of abstraction.