I agree with everything you say. My only understanding of the slowness of all this is that because Marion was never declared formally 'missing presumed dead' and there has never been a ruling that AKA was involved in her being missing, that procedurally murder detectives or the equivalent of the FBI / Interpol don't have the correct legal grounds to put a warrant for his arrest and questioning. Because of that, things have to be done slowly with every 'i' dotted and every 't' crossed - slowly, slowly, to catch the rare testicle-warbler in his natural habitat surrounded by his offspring.
Quite why the outcome of this Inquest is taking a year and a day, I'm not clear upon. I can't remember whether AKA had legal representation in the end. I think he did, didn't he?
According to Google, Australia has the Australian Federal Police (AFP) and the Australian Secret Intelligence Organisation (ASIO). In the UK where some of this took place, there's the National Crime Agency, International (NCA) and also MI5, MI6. Internationally, there's 196 countries of this world working with Interpol committed to fighting crime. There's also the LE and detection systems of the other countries he was in such as Belgium, Luxembourg, Holland.
I have a suspicion that nothing can move forwards until the Inquest declares Marion missing presumed dead after an entanglement with a man called '<insert current name>' (let's face it, he's changed his name again already hasn't he?) who has been established as a romance scammer and con artist and was involved in her disappearance. It will take a LOT of evidence for them to make that strength of statement. They may not be able to.
If that statement gets made, then all the other stuff can kick in but not before.
In terms of how the crime agencies spend their time, RB is small fry as they're probably looking a huge people trafficking rings, drug manufacturing and shipments, child trafficking, slavery, terrorism, arms dealing, money laundering, on and on.
JMO MOO