If we can equate an article that could be irrefutably tied to AE or FN with 'aircraft' wreckage (note in bottle in AE's handwriting, a known and distinct personal item, etc.) that is precisely what TIGHAR seems to still search for - as do others who search elsewhere. Short of that all we have is some level of confidence based on our own perusal and judgment.
It would be nice for some so-far not-found fire feature to have a bottle with a faded note in it written and signed by AE and / or FN in their handwriting... 
Well in this case given the problem that there is no real cultural differences in the material assemblage on the island, i.e. basically all are what you would expect from a mix of European influenced Islander debris and straight Western origin, then you would have to have something with 100% provenance to the missing fliers.
To date all the material evidence that TIGHAR have advanced to support their case lacks that crucial direct attribution and that is why there is so much debate and the lack of resolution. If TIGHAR comes up with something from the videos that requires the same level of reconstruction as the Bevington object to make a case then clearly that will not be accepted as anything more than a possible demonstration that their hypothesis is correct. It will be in the same category as the reassessment of the skeletal data which we know did not meet uniform acceptance, or the various attempts to link some artifacts like the freckle ointment jar to Earhart etc. The simple reason for this judgement is that second party reconstructions and possible attributions are not primary evidence - they are at best informed guesses.
That is wisdom itself I think. Much that we have is tantalizing - but even the best among that inventory is ambiguous enough to leave us in the fix of not having proven the hypothesis. Back to the note in the bottle in the fire feature... 
Now I may be wrong but I doubt that after 23 years or so TIGHAR want the same state of limbo to continue anymore than anyone else interested in the fate of Earhart and Noonan. But if the video shows what is clearly and unmistakably an engine or some major structural component of the Electra then that is the answer right there - clear and indisputable. Or, failing that, the next trip finds some directly attributable artifact or skeletal material on the island then that also is the answer to the question. However if they don't find either then the puzzle remains - I don't think after all this time and effort that TIGHAR wants that because ultimately time and natural decay will eventually remove any evidence that remains, wherever it may be.
There is one article that might yet turn out to be the long sought after smoking gun: the sextant box found
with the castaway's remains. We don't have the box, but we do know that it had two numbers written on it, and the idea that these numbers indicate USNO and manufacturer's serial numbers of the sextant the box once held seems likely to be essentially correct.
If a chain of custody of a sextant having those two numbers can be traced to FN/AE then I'd say we have our smoking gun, on the other hand if the chain of custody is traced to the navigator of the
S.S. Lovee, a schooner which was lost at sea in 1932 on a three hour cruise from Fiji with millionaire Thurston Howell II aboard , then Tighar would have lost the most evocative clues ever found on Gardner, i.e., the castaway and the sextant box. I think Malcom is correct in his assessment of the degree of proof offered by all the other artifacts found on Niku.
The chances of finding a record of, much less tracing the fate of, USN surplus sextant serial number 3500/1542 are probably slim to nil; most likely the key documents were taken from a warehouse and burned back in '40, along with Rosebud. But there is a slim chance that somewhere out there, in US government records, the records of some shipping company, the family posessions of Thurston Howell IV

, or somewhere else, those records still exist. Maybe they're available on the web, maybe they're available on paper in an archive. As slim as this possibility may be, it is the one possibility that all readers of this forum can investigate; they don't need to raise funds to rent a submersible, they don't need to fly to Fiji and convince authorities to let them look around governement buildings looking for bones.
If this piece of perishable information hasn't yet gone the way of Rosebud then you dear reader can be the one to prove the Niku hypothesis!....