Could you please elaborate on why Rust would be better than Go? Doesn’t Go offer good support for parallelism, which would be great use for implementing GNU Parallel.
Speed wise they are comparable to GNU Parallel. So the argument for Rust could be speed.
The argument against Rust could be backwards compatibility: How would you do the {= perl expr =} thing? Will it run on the current targets (CentOS 3.9 according to https://www.gnu.org/software/parallel/parallel_design.html#O...)? Will it run on systems for which you as a consultant do not have access to a Rust compiler for?