Well my approach is a fundamental shift in how we would run a Nix evaluation, based on 10 years of being annoyed at how costly evaluation can be sometimes, and the experience I gained in that time from Nix and software engineering in general.
So far includes two components, a novel Nix module system that actually provides sensible boundaries for Nix code for not much cost (it is actually insanely fast compared to the NixOS module system). This piece makes the Nix code bounded and trvially statically analyzeable. It perpusefully bucks the trend of depending on nixpkgs and being super complex and heavy. The core of it took me two hours to write and I have kept it purposefully small since. Besides performance and predictability, another nice feature is trivial tracing (unlike the monsterous traces produced by the nixos module system). There is still some work to do to integrate it more cleanly with my CLI, and I am almost at that stage.
As for the Rust based cli, there are a few core planned features but right