It's a great concept, but languages like Rust (https://www.rust-lang.org/), Zig (https://ziglang.org), Vlang (https://vlang.io/), etc... are already running with a similar idea to being easy to interact with C and are viable alternatives to it as well. Vlang even created its own OS, Vinix (https://github.com/vlang/vinix), to show its capabilities in this regard.

Seems to me, Cello would be more for those C programmers that didn't want to try the various alternative languages that are now out, and happen to agree with its developer's interpretation of preferred higher level abstractions and what they should look like. The point of these alternative languages is to offer features that C doesn't have or to implement them in easier or clearer ways.