Salve,
Just this week I got my hands on MJ Vermaseren's
Cybele and Attis, the Myth and the Cult
And I just began reading it today, but I found a part that somewhat supports a State Cult vs an Oriental Cult.
In ancient Athens, when the Official State Cult of Cybele was established Her shrine was located in the Agora whereas later a sanctuary was also set up as a private institution in Piraeus, the port town of Athens, by a group of foreignors (most likely the Asiatic Galli) in the fourth century BCE.
Though not directly proving the possibility of the Roman State vs Oriental Cults, it does give us some background making it all the more logical.[/u]
Another quote from the same book:
"Herculaneum has yielded an inscription dated 1 January 76, in which the emperor Vespasian announces that he has rebuilt the Cybele temple after the earthquake of the year 62 (templum Matris deum terrae motu collapsum restituit). Here the emperor is acting as the official representative of the Roman State cult."
You are right on track!