HA considerations when replicating data from a 12.1 database to a 10.2 database

My customer has a 12.1 database, protected by a physical standby on a different site which is kept in line with the primary using Dataguard. Some data from this database is replicated to a 10.2 database, also protected by a physical standby, using OGG. Now, as I understand it, OGG cannot replicate directly between a 12.1 and a 10.2 database – we have to use different versions of OGG on the source and target databases. Hence, an intermediate 11.2 OGG installation is in place, on which the OGG replicat process runs, updating the target 10.2 database remotely. Each site,