You might be interested in Guy Steele’s talk “It’s time for a new old language”. He talks about similar notations and the problem of inventing new ones (although most of his talk is about things other than BNF-like notations : he just talks about them for a bit in the beginning). It’s an interesting talk and is useful in thinking about proposing new notations.

YouTube: https://youtu.be/7HKbjYqqPPQ

If you search for the talk title you can find the PDF of the slides.