You could. But now you are trusting an entirely new toolchain that can build the Rust-based linker, even if it is statically linked. This toolchain is much larger than a comparatively small and much more easily understood C bootstrap toolchain.
This effectively triples or quadruples (maybe even more) the amount of code you need to trust for the cold bootstrap.
This effectively triples or quadruples (maybe even more) the amount of code you need to trust for the cold bootstrap.