Some users want to be able to test out MariaDB by introducing it into existing replication hierarchies that use MySQL GTID. Some of these users thought it would be useful for these kinds of scenarios if MaxScale's binlog router could convert MySQL's GTID events to MariaDB's GTID events (and possibly vice-versa as well).

MaxScale's binlog router currently does not even support replicating with MariaDB's GTID, so I would understand if that would need to be implemented before some GTID conversion mode could be implemented.