I don't think it's hare-brained, I think it'd be great. No less hare-brained than storing stuff to disk in any other format like json or yaml.
That said, the ergonomics are absolutely awful for modifying existing objects; you can't modify an existing object, you need to serialize a whole new object.
There's also a schemaless version (flexbuffers) which retains a number of the flatbuffers benefits (zero-copy access to data, compact binary representation), but is also a lot easier to use for ad-hoc serialization and deserialization; you can `loads`/`dumps` the flexbuffer objects, for example.
That said, the ergonomics are absolutely awful for modifying existing objects; you can't modify an existing object, you need to serialize a whole new object.
There's also a schemaless version (flexbuffers) which retains a number of the flatbuffers benefits (zero-copy access to data, compact binary representation), but is also a lot easier to use for ad-hoc serialization and deserialization; you can `loads`/`dumps` the flexbuffer objects, for example.