I've been thinking again about the identity of Oberhauser and I'd like to offer the following scenario. And I promise it has nothing to do with the general brouhaha on another thread involving leaks. I really have thought about this.
1) Franz Oberhauser really is Ernst Stavro Blofeld. Nothing to do with stolen identity. And the reason is;
2) Hannes Oberhauser's real surname is Blofeld.
Which may very well upset those of us who read the short story Octopussy. How can the father of the head of SPECTRE have been Bond's mentor? Well........
In this rebooted era, Blofeld senior and his (Greek?) wife defect from the Eastern Bloc, together with son Ernst. They settle in Austria with new identities after dad has spilled the beans about whatever Western intelligence was interested in. (Which would provide a very loose link to the original Thunderball novel, in which we are told that a SPECTRE board member with scientific leanings settled in the Alps after defecting from the East.)
"Hannes Oberhauser" adapts to his new life in Austria, is present when Andrew and Monique Bond die in a climbing accident, and takes their son James under his wing. There's no hint that Hannes is a wrong 'un - far from it. On the other hand, his son "Franz", having realised (As in the book Thunderball) that there's money to be made from "knowing the truth before the next man", sets out on his life of crime.
Decades pass, until "Franz" - who is now confident enough to revert to his birth name privately or within his immediate circle, the Quantum syndicate, whilst still using "Franz Oberhauser" to the outside world - realises that the British agent who has foiled the plans of Quantum and has effectively blown it as an organisation is, by a (very) strange co-incidence the same man who as a youngster was befriended by his dad. By now Quantum=SPECTRE, assuming it wasn't that all along. And so, using this knowledge, a trap is set for Bond, with Blofeld playing on his other identity to the hilt until Bond is well and truly snared. The trap might be the main aim or an additional refinement to a more grand, SPECTRE style plan. Whatever.
It might seem the daftest idea I've come up with since 2012 when I suggested that a new M might take over in the film SF and prove to be a baddie. But it gets around the "assumed identity" stuff I and others have posted about recently when it comes to Blofeld in this new film. Oberhauser = Blofeld, not because of identity theft or some other reason, but because his dad Hannes was also.