The multiple scripts per variable thing is implemented in Rust via a lint. For the explicit enabling of single scripts, I have suggested that for Rust, but sadly people preferred allowing all identifiers (while giving an option to only have ascii but I'd argue this is unfair for anyone who only wants to use a specific non-ascii language, why do they have to suddenly allow all languages in their code base?). There are also practical concerns, like who says what a language is, which characters it contains, how that language is called, etc? Someone has to maintain all these lists.