I hear you. The problem is that it doesn't make architectural sense for a qa_db_* function to do anything other than access the database. The problem arose because I didn't originally think ahead enough to create an app-level blob reading function, separate from the database one - sorry about that.
My best suggestion is to update the plugin to use code like this:
$content=function_exists('qa_read_blob') ? qa_read_blob($blobid) : qa_db_blob_read($blobid);
That way it will be compatible from Q2A 1.4 to 1.6 and beyond.