However, if you were entertaining the idea of slowly switching to Zig, the build system would be the place to start. Moving away from CMake is worth it even if you don't push it further.
But yeah, the C-Zig interop story is so good it's a no brainer if you want to "modernize" your C codebase, and you can do so incrementally instead of stopping the world for a rewrite.
Any rewrite is massive friction, I’m sure probably meant port? The only annoyance with Rust ports is if you have to support varargs. Hopefully that will come to an end soon.
Sadly, this is the general trend with neovim in general: less focus on stability, more and more focus on shiny new things. If I didn't have an nvim config that I'm used to I would have switched to plain vim ages ago.