>>I suggest creating an MDEV spec for COLUMN_BSON() to return BSON data which can handle binary (MongoDB uses it to store binary data). 

Nice, solve a binary representation problem, maybe we will need BSON_TO_COLUMN and JSON_TO_COLUMN too

>>In the same MDEV, COLUMN_JSON should be modified to omit binary columns and return a warning to use COLUMN_BSON for a complete representation of the data. 

I think we should extend the COLUMN_JSON function

instead of 

COLUMN_JSON(  dyncol ) 

"we" could have:

at binary_output we explain how binary values will be returned:

'raw'  -> do what COLUMN_JSON do today

'buffer'  -> like node.js encoding binary as array [12,34,52,42,123, etc ...]

'null' -> return NULL

any binary_output 'conversion' should report a warning that we have 'binary casting' with column_json function

or maybe, a warning to use column_bson function