Using BSON instead JSON will unlikely help with MongoDb because it already uses BSON everywhere. MongoDb is not tied to human readable JSON.
See Documents section in documentation
Document Format MongoDB stores documents on disk in the BSON serialization format. BSON is a binary representation of JSON documents, though contains more data types than does JSON. For the BSON spec, see bsonspec.org. See also BSON Types.
The mongo JavaScript shell and the MongoDB language drivers translate between BSON and the language-specific document representation.