A lot of desired features of the audit plugin are stalled as the current API doesn't provide necessary capabilities.
The list of desired ones:

• plugin data can be stored in the server table.
• information about user's role
• information about the tables/databases involved with the query
• possible parser result of the query
• export JSON functions
• access to the information about the connection
  encryption used
  authentication method
  connection type
  connector used

I don't think there is any reason to extend the structures that are sent to the auditing
fucntions. The way to go is creating server functions that can be linken in the plugin - irectly or via the 'service'-s.