> I really want a language that is memory and thread safe, but culled, honed and cut down to the absolute minimum language, to reduce the learning curve.

The problem is the syntax around the borrow checker is the learning curve. And if you cut out that, you are basically back to plain-old-C.

What are the “six sublanguages”?

Your question also doesn’t include if you are willing to compromise on any of Rust’s goals. Doing so would certainly let you make a simpler language, but then you don’t have what makes Rust Rust.

Here’s an example of someone who was involved in the design of Rust for a long time grappling with this question: https://boats.gitlab.io/blog/post/notes-on-a-smaller-rust/

Why not just use one of the dozens of available alternatives?

Go sounds like what you're after. Or perhaps Java. Both are much simpler, memory-safe languages (with arguably other trade-offs). Or maybe Erlang?

Swift is what you are looking for then? It has same goals as Rust(the original creator of Rust is(was?) working on Swift).