Which “marbles”? Rust is as much of a service ecosystem (crates.io, docs.rs) as it is an implementation of the Rust programming language.
The BSDs, for better or worse, didn’t have this problem because they mostly forked in the 90s and early 2000s. There were fewer (beneficial!) ecosystem assumptions.
And besides, this assumes that anybody really wants to do something as drastic as fork. I’m not privy to any of this, but it seems like the most “extreme” public position is nowhere close to forking Rust itself.
Just fork the project, collaborate online over git and get rid of all the bureaucracy/bureaucrats. This used to be quite common (that's why we have so many BSD distributions).