Refactoring the topology is a matter of a simple drag & drop. Orchestrator will keep you safe by disallowing invalid replication topologies
(e.g. replicating from ROW based to STATEMENT based, from 5.5 to 5.1 etc.)
Orchestrator is developed at Outbrain to answer for the difficulty in managing replication topologies.
At the time of orchestrator creation GTID is available via MySQL 5.6 and MariaDB 10.0. And yet GTID is still not as mature as one would hope for.
The majority of users still use plain-old binlog file:position based MySQL replication, and apparently this will hold for some time.