I read the suggestion as being about a new syntax for the existing language C++. For that you'd need 'only' a transpiler (and syntax high-lighter in your favorite support tools), quite possibly written in a readily available language, perhaps even C++. That should address your concerns regarding availability on various platforms and optimization. Your other concerns of course stand.

I, for one, find different languages with similar appearance needlessly confusing. I what the experience with different syntaxes for the same language would be.