Similar to how current default ASA parser is accommodating the PIX and other modules like FWSM, consider enhancing the parser to handle FTD Syslog message as well
Reference Firepower Syslog
Reference CISCO ASA
https://www.cisco.com/c/en/us/td/docs/security/asa/syslog/b_syslog/syslogs1.html#con_8584413
101001
Error Message %ASA-1-101001: (Primary) Failover cable OK.
101001
Error Message %FTD-1-101001: (Primary) Failover cable OK.