I feel like the comments are the only important part. I’d rather not have single quoted strings or unquoted identifiers to be honest. Trailing commas are nice to have though.
All I miss in JSON are comments and a native datetime type. Everything else, I’m fine with.
For comments, adding "_comment": "..." fields can work pretty well.
IMO it would be great if fields could have annotations for types that fall back as strings. Datetimes could be annotated for easier parsing.
Strongly disagree about datetimes; they exist at a different semantic level and are entirely too easy to get wrong.