Unpopular take: Sara Ellis and Alex Hunter should have always had split the treasure from the very beginning
Alex Hunter had always known about it due to her grandfather and had been looking her entire life. Edit: Alex even had the original password so all she had to do was to headfake adler and just entered the password herself with absolutely 0 risk.
Sara Ellis did all the original leg work, going to Argentina, checking for Uboats, etc.
The men Neal, Mozzie, even Peter - their involvement were purely accidental (they wouldn't have even found the boat without adler kidnapping them).
Sara and Alex should have split the treasure. Sara would have turn her portion in and gotten 20% on value of her potion, and Alex would have liquidated her lot with enough to buy a mansion on Lake Como and retire to Italy forever.
Also, without Peter's involvement, there would have been absolutely no legal issues with the discovery. The jeopardy only arose because Mozzie pretended to blow it up, not because of the treasure itself. So Alex and Sara would have had absolutely no legal troubles, true salvage!