Wilco - Question 1: How much would it cost to get this aircraft recovered and inspected?
Probably not as much as leaving any doubt related to what exactly happened to the people and the aircraft. The QPS seemed to be prepared to conduct a full investigation, but they were 'shoo'd' off by CASA, twice. Seems the second dive was at the Coroners insistence but limited to the FOD shield condition. It's only a feeling gleaned from the limited information available but the QPS seemed to want to keep digging. Perhaps, in the end they may be proved right. We will never know.
Wilco - Question 2: How will the Coroners report affect a civil case?
That is literally the $1,000,000 question; in any event with the amount of wriggle room being left open to the waring legal teams and insurance companies, it will be years before the answer is known. It seems to take forever when the issues are clearly defined, but in this mess – no bets taken.
Question 3: Who will finance a civil case and what will this cost?
Another tricky question, for which it seems there is no finite answer but, here again given the size and amount of holes in the cheese it will probably be a long time before resolution. But whatever happens in the legal future will very much depend, once again, on the Coroner. It's a sad, tough job made more so by an apparent lack of clarity and probity.
Maybe the whole thing should be turned over to the QPS and an independent report made to the Coroner; this would (IMO) – in the end – save tears, time and money. Perhaps not.