Caveat: If no operation is found in the properties file, the CoordinateOperationFactoryUsingWKT (well, in fact, the DefaultCoordinateOperationFactory) will generate a "standalone" transform, not searching for further trasforms in the EPSG database. Added a testDefaultBehavior showing the case (it uses a NTv2 transform, which needs BETA2007.gsb).
So, in a previous approach, I tried to call the "next available factory" from inside CoordinateOperationFactoryUsingWKT, before returning the control to DefaultCoordinateOperationFactory:
...and that worked, except when forcing LongitudeFirst.
Now, we need the DefaultCoordinateOperationFactory to try to split the operation into steps (from projected to geodetic, etc), but need also to prevent it to resolve a datum shift without previously visiting the EPSG database.
I'm willing to code, but some architectural view will be of much value. Any suggestions on how to do this neatly?