I would suggest the author also look at Amazon Ion:
* It can be used as schema-less
* allows attaching metadata tags to values (which can serve as type hints[1]), and
* encodes blobs efficiently
I have not used it, but in the space of flexible formats it appears to have other interesting properties. For instance it can encode a symbol table making symbols really compact in the rest of the message. Symbol tables can be shared out of band.
* It can be used as schema-less
* allows attaching metadata tags to values (which can serve as type hints[1]), and
* encodes blobs efficiently
I have not used it, but in the space of flexible formats it appears to have other interesting properties. For instance it can encode a symbol table making symbols really compact in the rest of the message. Symbol tables can be shared out of band.
[1] https://amazon-ion.github.io/ion-docs/docs/spec.html#annot